700025559
FIELD OF INVENTION
■ [0001] The present invention relates to a NOx reduction mechanism from an internal combustion engine and more particularly to NOx reduction by using a throttle controlled self-regulating recirculation.
5 BACKGROUND OF INVENTION
[0002] In general, an exhaust gas is emitted through a combustion process. The
exhaust gas is actually a combination of many different gases like N2, C02, CO, H20,
NO, and N02etc. Thoughjsome are hlafm less, few are harmful and are considered major
pollutants. NO, and N02 (combined called as NOx) are produced due to high
10 temperature inside the combustion chamber. Devices for treating some components of
exhaust gases (like HC, CO) uses the oxidation catalytic converters thereby these components are reduced from the exhaust gas. Exhaust gas recirculation (EGR) reduces NOx (NO, and N02) production during the combustion of fuel air mixture by reducing flame temperature.
15 [0003] The existing technology utilizes secondary air injection (SAI), optimized
catalytic converter for treating exhaust gases coming out of the combustion chamber. This particular method of injecting secondary air can though decrease the CO component, but above-mentioned configuration leads to high NOx emission. Introduction of EGR will reduce NOx largely and has reduced combustion noise. Spark
20 timing optimization with optimized EGR flow rates can reduce NOx while maintaining
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fuel consumption at current levels. Various mechanisms for EGR to reduce the NOx in the exhaust gases are already known.
SUMMARY OF THE INVENTION
[0004] To obviate the limitations of the prior art to reduce the quantity of NOx
5 emissions, a mechanism to reduce the amount of NOx in the exhaust gas is disclosed. In
the disclosed invention, a metered quantity of the exhaust gas is re-circulated back to
the inlet of the engine through the carburetor. A pre-calibrated orifice is used as a
metering device. This orifice is optimized for regulated exhaust gas recirculation based
upon the engine cylinder volume. This optimized amount of exhaust gas recirculation
10 dilutes the fresh charge and hence reduces oxygen availability and thereby reducing
peak combustion temperatures.
[0005] The main element of the current invention is a provision in the exhaust
system near the engine exhaust outlet to take a small sample of exhaust gas and route it
back to inlet of the engine. The sample of exhaust gas is transferred from the engine
15 exhaust outlet to engine inlet through a coiled pipe, which reduces the exhaust gas
temperature and provides a relatively cooler EGR sample. A provision is provided in the carburetor (before the throttle plate, on the inlet side of the throttle plate) for introducing the EGR'sample.
[0006] Benefits of the invention are NOx reduction with no modification in the
20 engine and minimum changes in vehicle exhaust system. The current invention also
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4
provides reduction of combustion noise at higher loads. Hence, a simple low cost
design solution is described. In yet another embodiment of the invention, an EGR
system with an electronic or pneumatic valve to control the rate of EGR at different
operating points of the engine is disclosed. The implementation of a variable valve will
5 give scope to switch off the EGR at idling and wide-open throttle, there by not effecting
cold starting and drivability.
BRIEF DESCRIPTION OF DRAWINGS
Figure lillustrates a typical two-wheeler.
Figure 2illustrates carburetor on engine of a two-wheeler. 10 - Figure 3 illustrates the side view of the carburetor.
Figure 4 illustrates the front view of the carburetor.
Figure 5 illustrates a perspective view of the carburetor.
Figure 6 illustrates the orifice in sectional view of the carburetor.
Figure 7 illustrates the block diagram of the EGR mechanism.
15 DETAILED DESCRIPTION OF THE INVENTION
[0007] The internal combustion engine has an intake and an exhaust system. The intake system comprises of an air filter and a carburetor. The fuel is supplied to the carburetor from the fuel tank. The exhaust system comprises of an exhaust pipe
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A
connected to the exhaust port of the engine. The exhaust pipe is provided with a
provision to tap exhaust gas and re circulate the exhaust gas into the carburetor inlet by
aid of a coiled pipe also called as EGR pipe. The EGR pipe is fitted to the exhaust pipe
near to the engine exhaust port. The EGR pipe is provided with circular coils with
5 number of turns to reduce the EGR sample temperature. The EGR pipe taps the exhaust
gas on one end and another end of the EGR pipe is connected to a provision on the carburetor. The provision on the carburetor to which the EGR pipe is attached is an integrated tube which has a projection outside the carburetor, the other end of tube ends at the inlet side of the throttle plate of the carburetor.
10 [0008] The carburetor has a. provision for EGR sample inlet. The fuel enters the
carburetor through a float mechanism. The part of carburetor which is connected to the air filter acts as air inlet to the carburetor. The outlet of the carburetor is. connected to the engine through a pipe. A throttle plate regulates the flow of air fuel mixture depending on the plate opening. When the throttle plate is at closed position which
15 corresponds to the low idle condition of the engine, the air fuel mixture is transferred
through a bypass orifice also called idle hole.
[0009] During idling condition, the required EGR amount is kept at minimum level.
A solid tube having a thorough hole is provided through the body of carburetor so that
its one end is outside the carburetor and the other end opens at the inlet side of the
20 throttle plate of the carburetor. The tube acts as the EGR tube. The EGR tube has a
threaded inlet for provision to fit a pre-calibrated orifice through which the EGR flow
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rate can be fixed. During idling, the throttle plate is closed and the EGR pipe is not connected to the outlet of the carburetor. Hence EGR is cut off during idling.
[00010] As the throttle plate opens, due to demand from the driver, air flow through
the carburetor increases and due to the venturi effect of the carburetor, on the intake
5 side, a low pressure zone is created due to which fuel is drawn along-with fresh air. At
the same time the exhaust gas through the EGR inlet pipe enters and mixes with the air
fuel mixture. The charge mixed with EGR leaves the carburetor and enters the engine
intake. The rate of EGR flow is proportional to the pressure drop across the exhaust
manifold and the throttle side of the carburetor. At .wide open throttle condition, the
10 vacuum suction pressure behind the carburetor throttle is lower as compared to part
loads; due to this the differential pressure of EGR and intake air is lesser. This reduces the EGR flow at wide open throttle condition.
[00011] A calibrated orifice is fitted to the inlet point of the carburetor where the
EGR pipe is fitted. The diameter of the orifice depends on the EGR flow requirements,
15 engine exhaust flow rates and NOx and fuel consumption criticality at various speeds
and loads.
[00012] Figure 1 illustrates a two wheeled vehicle 10, with fuel tankl, rider seat 2,
rear wheel 3, centre stand 4, an internal combustion engine 5, front wheel 6, front
suspension 7 and head lamp 8. The fuel from fuel tank is supplied to the sump of the
20 carburetor from where the fuel is ejected into outlet of the carburetor by venturi effect
along with the air.
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[00013] Figure 2 shows the engine 5 mounted on the vehicle in-between the vehicle
frame members 21 and 22. Figure 2 also shows the cylinder head 24, cylinder block 25
and the carburetor 26. Carburetor 26 supplies the air-fuel mixture to the engine 5 inlet.
The exhaust port of the engine is attached to the exhaust pipe to carry out the exhaust
5 from the engine to the outer atmosphere. Exhaust pipe near to the exhaust port end has
an exhaust tapping point to tap the exhaust gas and send it to the carburetor EGR tube which is described further in a more detail in the description.
[00014] Figure 3 illustrates the side view of the carburetor26. Figure 3 shows the carburetor top 30, throttle lever 32, and throttle adjustment screw 34. During operation,
10 the fresh air enters the carburetor from the end 31 and leaves the carburetor from the
end 33 which further enters the engine inlet. The throttle lever 32is connected to a throttle plate (described in a more detail in Figure 4). The throttle lever 32 can be rotated by help of a wire which is further controlled by the driver by his/her fist rotation. The screw 34can be adjusted to provide initial default opening of the throttle
15 for regulating adequate amount of air entry inside the combustion chamber of the
internal combustion engine for proper combustion of the fuel.
. [00015] Figure 4 illustrates the carburetor 26 with throttle lever 32, EGR tube 41,
throttle plate 42, throttle adjustment screw 34 and EGR tube axis AA'. The axis AA' of
the EGR tube 41 is maintained in such a way so as to pierce the carburetor and the
20 other end of the EGR tube 31 is behind the throttle plate 42, which is also the inlet side
of the throttle body of the carburetor.
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[00016] Figure 5 illustrates a perspective view of the carburetor 26. Figure 5 shows
EGR tube 41, throttle plate 42, orifice hole 51, EGR tube thread 52, and the throttle
body 53. The EGR tube 41's end inside the carburettor's throttle body is the orifice
hole 51. In zero throttle condition, the throttle plate 42 blocks the throttle body so no air
5 fuel mixture passes through the main passage of the throttle body. Though during this
condition, idle hole allows passage of fuel. The throttle plate may be provided with a small setting for air to pass through the throttle main body as air is necessity for sustaining the combustion inside the internal combustion engine.
[00017] The. location ofc.orifice 51 -is -optimized in such a way that during zero
. 10 throttle condition, the orifice hole 51doesn't facilitate the passing of EGR through the
throttle main body to the inlet of the internal combustion engine. Since the throttle plate
■ 42 rotates about a spindle inside the throttle main body, a small rotation of the throttle
plate exposes the orifice hole 51 to the throttle main body and EGR can get mixed with
the incoming air fuel mixture and hence be fed to the inlet of the internal combustion
15 engine. Moreover, the distance between the throttle plate42and the orifice hole 51 at
zero throttle pan be optimized to bring the EGR into action at any predetermined
throttle angle.
. [00018] Figure ^illustrates the sectional view of the carburetor 26, the section planes
being taken along the EGR tube 41, orifice hole 51and a plane parallel to the throttle
20 plate 42of the carburetor26.As shown in the Figure 6, the throttle plate 42 divides the
throttle body of the carburetor in two halves. Out of the two halves, the first half is inlet
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EGR64 and the other half is outlet EGR65. The region for inlet EGR 64 is before the
throttle plate and the region for outlet EGR 65is after the throttle plate 42 as seen from
the directions 31to33 of flow of air fuel mixture. As shown, the idling hole 63is used to
provide the air fuel mixture to the engine intake during idling condition. As disclosed in
5 the current invention, the EGR tubes 41feeds exhaust gas to the throttle of the
carburetor before the throttle plate. The distance 62 between the throttle plate 42and the orifice hole 51 can be increased or decreased as per the requirement of opening EGR at a lesser or greater throttle opening.
[00019] FigureXshaws a.schernattc.blqck diagram of the EGR mechanism as,per the
10 current invention. The air-filter 71 provides fresh filtered atmospheric air to the
carburettor 26 through the duct 76. The filtered atmospheric air after passing through
the carburetor 26is sent to the engine 5. The exhaust gases are expelled from the engine
5 through the exhaust pipe 74(27) on which an exhaust tapping 77(28) is provided. The
tapped exhaust gas is passed through the pipe 74 which has a curled profile 78 from
15 which the exhaust gas is fed to the carburetor throttle plate inlet side. Fuel tank 1
provides fuel to the carburetor through a different path 72.
20 fe*T>. d>avt
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700025561

We claim:
1. A system of exhaust gas recirculation for an internal combustion engine (5), the internal combustion engine (5) comprising:
an intake pipe to carry an air fuel mixture for combustion into the internal
5 combustion engine (5);
an exhaust pipe (27) to carry exhaust gases out of the internal combustion engine (5), wherein a provision (28) is made on the said exhaust pipe (27) for tapping exhaust gas for recirculation (EGR);
Tcarburetor"(26Vwith a throttle plate (42) to control the flow of the air-fuel
10 mixture;
wherein the said provision for exhaust gas recirculation tapping (28) is connected to a first end (66) of an orifice body (41) extending out of the carburetor (26) and a second end (67) of the said orifice body (41) is exposed on the inlet side (31) of the said throttle plate (42).
15 2. ^The system of exhaust gas recirculation for an internal combustion engine (5) as
claimed in Claim 1 wherein the said orifice body (41) is at a predetermined distance from the throttle plate (42)-as per requirement of EGR activation at a particular throttle.
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3. The system of exhaust gas recirculation for an internal combustion engine (5) as claimed in Claim 1 wherein the said exhaust pipe (27) for EGR tapping is curled before connection to carburetor (26) for cooling the exhaust gas.
5 4. The system of exhaust gas recirculation for an internal combustion engine as
Claimed in Claim 1 wherein the portion of orifice body (41) which is extending outside the carburetor (26) has threaded portion to accommodate an orifice hole (51) of a predetermined size.
10 5. The system of exhaust gas recirculation for an internal combustion engine as
Claimed in Claim 1 wherein the orifice body (41) does not provide the exhaust gas recirculation during engine idling condition.