SYSTEM FOR COOLING AND RE-CIRCULATION OF DILUTE MIXTURE OF EXHAUST GAS AND CHARGED AIR TO AN IC ENGINE

FIELD OF THE INVENTION

The present invention relates to the fields of exhaust gas re-circulation (EGR) system for an internal combustion (IC) engine of a motor vehicle. The present invention specifically relates to an improved system for cooling and recirculation of dilute mixture of exhaust gas and charged air to the IC engine.

BACKGROUND OF THE INVENTION

Currently, cooled exhaust gas recirculation (EGR) systems are used in the IC engines of the motor vehicle for meeting exhaust gas emission regulations, i.e. for reducing nitrogen oxide emissions (NOx). It is necessary to maintain emission level of the oxides of nitrogen pollutants within legal limitations and regulations of emission norms. Such EGR systems receive and cool the exhaust gas from the IC engine and re-circulate the exhaust gas mixed together with charged air, again to the IC engine. The re-circulated exhaust gas to the IC engine reduces the oxygen content corresponding to the quantity and consequently the maximum gas temperature during combustion is held at an optimum level by not exceeding the oxides of nitrogen pollutants beyond the legal limits.

FIGS. 1 & 2 illustrate a schematic diagram of conventional low pressure and high pressure EGR systems for a turbocharged IC engine, respectively, in accordance with a prior art. The EGR systems are classified by means of introduction of the exhaust gas by an external arrangement or by an internal inbuilt arrangement on the engine. The external EGR systems are further classified by the location of mixing point of exhaust gas and charged air, by which it is refereed as high pressure EGR cooling system and low-pressure EGR cooling system. If the exhaust gas is introduced before a turbocharger, then the EGR systems are referred as low-pressure EGR systems whereas, if the exhaust gas is introduced after the turbocharger, the EGR systems are referred as high-pressure EGR systems. In case of naturally aspirated engines, the low-pressure EGR systems are only applicable. The conventional EGR systems are associated with an engine 101 having an intake manifold 102, an exhaust manifold 103 and a fan 104.

In case of conventional low pressure EGR system as shown in FIG. 1, the exhaust gas from the exhaust manifold 103 is carried to a turbine 105 for driving a compressor 110 of the turbocharger. Then, the exhaust gas is passed to an EGR cooler 108 through a catalyst 106 and an EGR valve 107 for cooling the exhaust gas. The cooled exhaust gas is mixed with charged air from an air inlet 109. The mixture of exhaust gas and charged air is passed to a charged air cooler (CAC) 111 after it is compressed through the compressor 110. The charged air cooler (CAC) 111 is placed in proximity to a radiator 112 of the vehicle. Finally, the cooled mixture of exhaust gas and charged air is re circulated to the intake manifold 102 of the engine 101.

Similarly, in case of conventional high pressure EGR system as shown in FIG. 2, the exhaust gas from the exhaust manifold 103 is bypassed to the EGR cooler 108 through the EGR valve 105, and also is carried to the turbine 105 for driving the compressor 110 of the turbocharger. The charged air form the air inlet 109 is compressed by the compressor 110 of the turbocharger and is passed and cooled in the CAC 111. The cooled charged air and the cooled exhaust gas are mixed at point of dilution, so that the mixture of exhaust gas and charged air is passed to the engine 101 through the intake manifold 103.

As illustrated in FIGS. 1 & 2, the exhaust gas are cooled by passing through the heat exchanger or EGR cooler 108 and the flow control valve 107 for maintaining the desired exhaust gas temperature and the quantity of exhaust gas to be re-circulated in the air intake. The CAC, which acts as a heat exchanger, is used to cool the boosted air charge from the turbocharger compressor outlet prior to entry into the intake manifold of the engine. The engine coolant in the heat exchanger cools the hot exhaust gas before it is passed to the engine. A separate EGR cooler is used to cool the exhaust gases using engine coolant before mixing it with charged air from the compressor 110 of the turbocharger through the CAC 111. This mixture of re-circulated exhaust gas and charged air is introduced into the intake manifold 102 of the engine 1 to enroute the mixture to an engine cylinder for combustion as required to reduce nitrogen oxides emissions from engine exhaust. In both of the conventional EGR systems, the exhaust gas is cooled by the heat exchanger and the separate, dedicated cooler for re-circulation in a controlled manner by an electronically or pneumatically controlled valve for its quantum and temperature by cooling using engine water, into the air intake of the engine to mix with the intake air.

With respect to conventional EGR systems, it is necessary to provide a separate, dedicated cooler for cooling the hot exhaust gas, which increases the number of parts and requires more space. The conventional EGR systems also suffer failures or faults in the EGR valve due to thermal loading by the hot exhaust gas from the engine or the formation of deposits from the exhaust gas, which increases warranty cost. Further, the point of dilution for mixing of re circulated exhaust gas and cooled charged air is achieved within the engine conduit, which results in improper mixture enters into the engine. Such improper mixture causes degradation in the operation and performance of engine and overall system. Therefore, it is desirable to provide an improved system is developed for system for cooling and re-circulation of dilute mixture of exhaust gas and charged air to an IC engine, which is capable to address and overcome the above disadvantages of conventional EGR systems.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a system for cooling and re-circulation of dilute mixture of exhaust gas and charged air to an IC engine, which achieves higher overall effectiveness of cooling and appropriate mixing of exhaust air with charged air to the IC engine.

Another object of the present invention is to provide a system for cooling and re-circulation of dilute mixture of exhaust gas and charged air to an IC engine, which eliminates the need for electronically controlled valve and independent heat exchangers or coolers for cooling the charged air and the exhaust gas re-circulated into the engine for emission control.

A further object of the present invention is to provide a system for cooling and re-circulation of dilute mixture of exhaust gas and charged air to an IC engine, which is cost effective and simple in construction.

According to one aspect, the present invention, which achieves the objectives, relates to a system for cooling and re-circulation of dilute mixture of exhaust gas and charged air to an IC engine comprises a turbocharger having a turbine and a compressor coupled together. The turbine is operated using exhaust gas from the engine to drive the compressor, which pumps charged air by compressing fresh air received from an air inlet unit. An orifice means is attached to an exhaust manifold of the engine for metering and regulating a desired quantity of exhaust gas in an exhaust gas recirculation (EGR) conduit. A venturi means is in connection with the orifice means and the compressor for diluting pressure of the desired quantity of exhaust gas and homogenously mixing the diluted exhaust gas with the charged air from the compressor in a uniform manner. A cooler unit is associated with the venturi means for cooling and recirculating the dilute mixture of exhaust gas and charged air to an intake manifold of the engine for combustion. The system achieves higher overall effectiveness of cooling and appropriate mixing of exhaust air with charged air to the IC engine and also eliminates the need for two independent heat exchangers and electronically controlled valve.

Furthermore, a filter is located in the EGR conduit between the orifice means and the venturi means for filtering soot particles from the exhaust gas. The orifice means is situated ahead of the turbine of the turbocharger and is configured to connect an exhaust conduit to the EGR conduit, which extends from upstream of the turbine to upstream of the cooler unit. The exhaust conduit extends from the exhaust manifold of the engine to the turbine of the turbocharger.

In addition, the venturi means is configured to control admission of the exhaust gas irrespective of load and speed conditions of the engine. The venturi means is placed at a point of dilution to connect an intake air conduit and the EGR conduit. The intake air conduit extends from the compressor to the intake manifold of the engine. The cooler unit is placed in proximity to a radiator and an engine fan for cooling the dilute mixture of exhaust gas and charged air. The exhaust gas from the turbine is passed to a catalyst for treating the exhaust gas before emission of the exhaust gas to atmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same.

FIG. 1 shows a schematic diagram of a conventional low pressure exhaust gas recirculation (EGR) system for a turbocharged IC engine, in accordance with a prior art;

FIG. 2 illustrates a schematic diagram of a conventional high pressure EGR system for the turbocharged IC engine, in accordance with a prior art; and

FIG. 3 illustrates a schematic diagram of a system for cooling and recirculation of dilute mixture of exhaust gas and charged air to an IC engine, in accordance with an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 3, a schematic diagram of a system for cooling and recirculation of dilute mixture of exhaust gas and charged air to an IC engine is illustrated, in accordance with an exemplary embodiment of the present invention. The present invention generally relates to a new and improved Exhaust Gas Re-circulation system, particularly high pressure filtered EGR system for the internal combustion (IC) engine. Hereafter, the system can be referred as EGR system only for the purpose of explanation. The EGR system is associated with an engine 1, which is assembled with an intake manifold 2, an exhaust manifold 3 and a fan 15.

The EGR system is normally arranged with a turbocharger having a turbine 6 and a compressor 9. The exhaust manifold 3 of the engine 1 is connected with the turbine 6 of the turbocharger, so that the exhaust gas from the exhaust manifold 3 of the engine 1 can be passed to run the turbine 6, which drives the compressor 9 of the turbocharger. Then, the exhaust gas from the turbine 6 is passed to a catalyst 7, which is employed for treating the exhaust gas before emission of the exhaust gas to atmosphere. The compressor 9 of the turbocharger receives fresh air from atmosphere through an air cleaner 8, which acts as an air inlet unit. The turbine 6 is operated by means of exhaust gas from the engine 1, such that the compressor 9 of the turbocharger is driven for compressing the fresh air from the air cleaner 8 to produce charged air 10, as shown in FIG. 3.

The EGR system is arranged with an exhaust conduit 16 extending from the exhaust manifold 3 of the engine 1 to the turbine 6 of the turbocharger, an intake air conduit 17 extending from the compressor 9 of the turbocharger to the intake manifold 2 of the engine 1, and an exhaust gas recirculation (EGR) conduit 18 extending from upstream of the turbocharger (before the turbine 6) to upstream of the CAC 13 (after the compressor 9). The EGR system comprises an orifice or orifice plate 4 that is interconnected with the exhaust manifold 3 of the engine 1 for metering and controlling the exhaust gas from the exhaust manifold 3 of the engine 1 to re-circulate a desired amount of exhaust gas to the EGR conduit 18. The orifice 4 is placed in the EGR conduit 18 and is positioned before the turbine 6 of the turbocharger. The EGR system also comprises a venturi 12 for enhancing a mixture of EGR gas and charged air, and an optional filter 5 provided in the EGR conduit 18 between the orifice 4 and the venturi 12 for filtering the EGR gas 11 before passing it to the venturi 12. The filter 5 is used to remove soot particles from the re-circulated exhaust gas.

Further, the venturi 12 is associated with the orifice 4 and the compressor 9 for diluting and mixing the desired amount of EGR gas 11 from the orifice 4 with the charged air 10 from the compressor 9 in a uniform manner. The dilute mixture, i.e. uniform mixture of re-circulated exhaust gas 11 and charged air 10, is then cooled by a combined charge air and exhaust gas cooler (CAC) 13 and re-circulated to the intake manifold 2 of the engine 1. In addition, a radiator 14 is connected fluidly to the IC engine 1 and positioned in proximity to the engine fan 15. The radiator 14 is placed behind or in front of the CAC 13 for cooling the engine coolant with the help of ambient air, which is pulled or pushed over to the radiator 14 by using the engine fan 15. The CAC 13 is positioned to directly receive ambient air in order to cool both re-circulated exhaust gas and charged air from the compressor 9 of the turbocharger.

In the operation of EGR system, initially the orifice 4 measures, guides and controls the quantity of the exhaust gas coming from the engine 1 and then allows the measured quantity of exhaust gas to pass through the filter 5, which traps soot particles from the exhaust gas 11. Thereafter, the metered quantity of filtered re-circulated exhaust gas 11 is introduced into the EGR venturi 12 placed at the point of dilution of re-circulated exhaust gas and fresh charged air from the compressor 9 of the turbocharger. The venturi 12 dilutes the pressure of the re-circulated exhaust gas 11 and mixes the re-circulated exhaust gas 11 with the fresh charged air 10 from the compressor 9 of the turbocharger. This dilute mixture of charged air and re-circulated exhaust gas is then cooled by passing it to the combined charge air and re-circulated exhaust gas cooler 13.

Thereafter, the cooled mixture of charged air and re-circulated exhaust gas is introduced in an engine cylinder for combustion by passing it to an engine combustion chamber through the intake manifold 2 of the engine 1. Thus, the present EGR system performs cooling of the charged air 10 from the turbocharger compressor 9 and the re-circulated exhaust gas 11 in a combined cooler, i.e. CAC 13, before re-circulating into the intake manifold 2 of the engine 1. Such arrangement of the EGR system eliminates two independent heat exchangers for cooling the charged air and the exhaust gas and achieves recirculation of the dilute mixture into the intake manifold 2 of the engine 1 for emission control without the need for any electronically controlled valve. It also achieves higher overall effectiveness of cooling and appropriate mixing of exhaust air with charged air to the IC engine.

The high pressure EGR system of the present invention does not employ a dedicated EGR cooler or EGR valve, which results in lesser number of parts, lower weight, more space availability, higher reliability and lower overall system cost. The EGR system uses the engine CAC for cooling the total mixture of boosted air and re-circulated exhaust gases, after the exhaust gas enters into the CAC intake pipe of the turbocharged intercooled IC engine and achieve emissions performance on any turbo charged after-cooled IC engines. This is applicable for both the engines fitted with water to air and air-to-air CACs. Thus, it avoids boiling as it is in the conventional EGR cooler, and provides a greater potential for cooling as larger temperature difference is maintained. It also achieves higher overall effectiveness of the cooling package as the heat is rejected to the atmosphere by exhaust gases at high temperature to the atmosphere. On the other hand, in the conventional EGR cooling system using the engine water or coolant, the heat is rejected from water at 95 deg Celsius to the atmosphere and hence the cooling package is less effective.

In addition, the EGR system employs the orifice to govern the amount of exhaust gas for re-circulation, which eliminates the need for an EGR valve and thus saves the highest warranty cost due to the failure of the EGR valve that is used in the conventional EGR system. The EGR system employs the venturi at the point of dilution of re-circulated exhaust gas with charged air from compressor of turbine for improving dilution and better mixing of re-circulated exhaust gas and cooled charged air by producing local vacuum, and also to ensure admission of EGR in the inlet irrespective of the load and speed conditions of the engine. The EGR system preferably includes the filter in the EGR conduit between the orifice and the venturi, where the filter of the EGR system may or may not be employed. Such EGR system can be implemented in motor vehicles for re-circulation of the cooled and regulated mixture of exhaust gas and charged air to the IC engine.

The usage of EGR system can be experimented without a dedicated EGR cooler, with an orifice for metering the EGR gases, with or without a dedicated EGR filter and with a venturi for homogenous mixing to achieve emissions performance on any turbocharged after-cooled IC engines. The research experiment is performed on a similar system in production employing the new EGR system, which confirms that the EGR system is feasible to achieve emission performance conforming to Indian BS III CEV emission norms without employing a dedicated EGR cooler cooled by engine coolant, using virtual simulations.

The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

WE CLAIM:

1. A system for cooling and re-circulation of dilute mixture of exhaust gas
and charged air to an internal combustion (IC) engine, comprising:

a turbocharger having a turbine and a compressor coupled together, said turbine is operated using exhaust gas from the engine to drive said compressor, which pumps charged air by compressing fresh air received from an air inlet unit;

at least one orifice means attached to an exhaust manifold of the engine for metering and regulating a desired quantity of exhaust gas in an exhaust gas recirculation (EGR) conduit;

at least one venturi means in connection with said orifice means and said compressor for diluting pressure of the desired quantity of exhaust gas and homogenously mixing the diluted exhaust gas with the charged air from said compressor in a uniform manner; and

a cooler unit associated with said venturi means for cooling and recirculating the dilute mixture of exhaust gas and charged air to an intake manifold of the engine for combustion.

2. The system as claimed in claim 1, further comprising at least one filter located in said EGR conduit between said orifice means and said venturi means for filtering soot particles from the exhaust gas.

3. The system as claimed in claim 1, wherein said orifice means is situated ahead of said turbine of the turbocharger.

4. The system as claimed in claim 1, wherein said orifice means is configured to connect an exhaust conduit to said EGR conduit.

5. The system as claimed in claim 1, wherein said EGR conduit extends from upstream of said turbine to upstream of said cooler unit.

6. The system as claimed in claim 4, wherein said exhaust conduit extends from said exhaust manifold of the engine to said turbine of the turbocharger.

7. The system as claimed in claim 1, wherein said venturi means is configured to control admission of the exhaust gas irrespective of load and speed conditions of the engine.

8. The system as claimed in claim 1, wherein said venturi means is placed at a point of dilution to connect an intake air conduit and said EGR conduit.

9. The system as claimed in claim 7, wherein said intake air conduit extends from said compressor to said intake manifold of the engine.

10. The system as claimed in claim 1, wherein said cooler unit is placed in proximity to a radiator and an engine fan for cooling the dilute mixture of exhaust gas and charged air.

11. The system as claimed in claim 1, wherein the exhaust gas from said turbine is passed to a catalyst for treating the exhaust gas before emission of the exhaust gas to atmosphere.