22-Jun-201‘iéil22237l3228-CHE-2015/Description(Complete)
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FIELD OF INVENTION
[0001] The present invention relates to a NOx reduction mechanism for an
internal combustion engine and more particularly to NOx reduction by using a
throttle controlled self-regulating recirculation using carburetor.
BACKGROUND OF INVENTION
[0002] In general, every combustibn process emits exhaust gases. In case of
combustion of petroleum based fuels, the exhaust gas is actually a combination of
many different gases like N2, C02, CO, H20, NO, and
N024 etc. Though some of
the gases are harmless, a few are harmful and considered as major pollutants. NO,
and N02 (combined called as NOx) are produced due to high temperature inside the
combustion chamber. A few constituents of exhaust gases (like HC, C0) are treated
by devices using oxidation in catalytic converters thereby these components are
easily reduced from the exhaust gases. The other remaining constituents of the
exhaust gases are reduced by exhaust gas recirculation. (EOR) process which
reduces NOx (NO, and N02) production during the combustion of fuel air mixture
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by reducing flame temperature.
[0003] Secondary air injection (SAI) and optimized catalytic converter are
known for treating exhaust gases. However, the method of injecting secondary air
decreases the CO component, but simultaneously leads to high NOx emission due to
high temperature. Furthermore, introduction of exhaust gases inside combustion,
chamber reduces NOx and combustion noise. In a known method, spark timing
optimization with optimized EGR flow rates can also reduce NOx while maintaining
optimal fuel consumption. 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 theprior art and to reduce the quantity of
NOx emissions, a mechanism to reduce the amount of NOx in the exhaust gas is
described herein. In the described invention, a metered quantity of the exhaust gas is22-Jun-2016/22237/3228¢CHE-2015/Description(Complete)
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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 dilutes the fresh charge, hence reduces oxygen availability,
and thereby reduces peak combustion temperatures.
[0005] The main embodiment of the current invention includes a provision in
the exhaust system near the engine exhaust outlet to take a small sample of exhaust
gasand route it back to inlet of the engine through carburetor spindle of a constant
vacuum carburetor. The exhaust gas sample is transferred from engine exhaust outlet
to engine inlet through a coiled pipe that reduces the exhaust gas temperature and
provides a relatively cooler EGR sample. Further, a provision is made in the
carburetor (before the throttle plate, on the inlet side of the throttle plate) for
introducing the exhaust gas sample.
[0006] Benefits of the invention are NOx reduction with no modification in the
engine and minimum changes in vehicle exhaust system. The current invention also
helps in reduction of combustion noise at higher loads. Hence, the present invention
provides a simple low cost solution. In yet another embodiment of the present
invention, an EGR system. with an electronic or pneumatic valve to control the rate
of EGR at different operating points of the engine is described. The implementation
of a variable valve will give scopeto switch off the EGR at idlingand wide-open
throttle, there by not effecting cold starting and drivability.
BRIEF DESCRIPTION OF DRAWINGS
[0007] Figure lillustrates a typical two—wheeler.
[0008] Figure Zillustrates carburetor on engine of a two-wheeler.
[0009] Figure 3 illustrates the block diagram of the EGR mechanism.
[00010] Figure 4 illustrates the front view of the carburetor.
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[00011] Figure 5 illustrates a perspective ‘view of the carburetor with EGR tube
according to the first embodiment of the current invention.
[00012] Figure 6 illustrates the orifice’s sectional view with the carburetor
spindle having EGR tube according to the first embodiment of the current invention
at 0% throttle.
[00013] Figure 7 illustrates the orifice’s sectional view with the carburetor
spindle having EGR tube according to the first embodiment of the current invention
at part throttle.
[00014] Figure 8 illustrates the orifice’s sectional view with the carburetor
spindle having EGR tube according to the first embodiment of the current invention
at 100% throttle.
[00015] Figure 9 illustrates a perspective view of the carburetor with EGR tube
according to the second embodiment of the current invention.
[00016] Figure 10 illustrates the orifice’s sectional view With the carburetor
spindle having EGR tube according to the second embodiment of the current
invention at 0% throttle.
[00017] Figure 11 illustrates the orifice’s sectional view. with the carburetor
spindle having EGR tube according to the second embodiment of the current
invention at part throttle.
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[00018] Figure 12 illustrates the orifice’s sectional view with the carburetor
4
spindle having EGR tube» according to 'the second embodiment of the current
invention at 100% throttle.
DETAILED DESCRIPTION OF THE INVENTION
[00019] An internal combustion engine comprises of 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 comprisesof anexhaust pipe connected to the exhaust port of engine. In oneembodiment of the
current invention, exhaust pipe is provided with a provision to tap exhaust gas
and to recirculate the exhaust gas into the carburetor inlet by aid of a coiled pipe
also called as EGR pipe. The EGR pipe’s other end is connected to the exhaust pipe
near to the engine exhaust port. The EGR pipe is provided with circular coils with
plurality of turns to reduce the EGR sample temperature. Hence, 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 one projection outside the carburetor
10 body while the other end of tube ends on the outlet side of the throttle plate of the
carburetor.
[00020] 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
15 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 corresponds to the low idle condition of the engine, a pre-determined amount
of air fuel mixture is transferred through a bypass orifice also called
idle.
hole. The
throttle plate is mounted on a rotatable spindle.
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t00021] The EGR tube having a thorough hole is provided through a slot on the
spindle of throttle plate of the carburetor so that its one end is outside the carburetor
and the other end opens on rotatable spindle on the outlet side of the throttle plate of
the carburetor. The tube acts as the EGR tube. In yet another embodiment, the EGR
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tube has a threaded inlet for provision to fit a pre-calibrated orifice through which
25 the EGR flow rate can be fixed. The diameter of the orifice depends on the EGR
flow. requirements, engine exhaust flow rates and NOx and fuel conSumptiOn
criticality at various speeds and loads. 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
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during idling. Hence, during idling condition, the required EGR amount is kept at
minimum level.
[00022] As the throttle plate opens, due to demand from' the rider, air flow
through the carburetor increases and due to the venturi effect of the carburetor, on
the intake side, a low pressure zone is created due to which fuel is drawn along-with
fresh air through the float mechanism. 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 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
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throttle condition.
[00023] 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, frontwheel 6, front
suspension 7 and head lamp 8. The fuel from fuel tank is supplied to the sump of -
- the carburetor from where the fuel is ejected into outlet of the carburetor by venturi
effect along with the air.’
[00024] Figure 2 shows [the
engine 5 mounted on the vehicle in-between the
vehicle frame
membersiiz2lli
and 22. Figure 2 also shows the cylinder head 24,
cylinderblock 25 and the carburetor 26. Carburetor 26 suppliesthe air-fuel mixture
to the engine 5 inlet. The exhaust port of the engine is attached to an exhaust muffler
to attenuate thenoise and to carry out the exhaust from the engine to the outer
atmosphere through a tail pipe. An exhaust tapping point to tap the exhaust gas is
made at a predetermined distance from the exhaust port _in the downstream direction.
The exhaust tapping point is connected to an exhaust pipe which is further
connected to the carburetorEGR- tube which is described further in a more detail in
the description.
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[00025] Figure 3 shows a schematic block diagram of the EGR mechanism as per
the current invention. The air filter 71 provides fresh filtered atmospheric air to the
carburetor 26 through the duct
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The filtered atmospheric air after passing through
the carburetor 26 is sent to the engine 5. The exhaust gases are expelled from the
engine 5 through the exhaust muffler which is connected to the exhaust port of” the
engine 5. An exhaust tapping point 77 to tap the exhaust gas is made at a
predetermined distance from the exhaust port in the downstream direction. The
tapped exhaust gas is passed through the pipe 77 which has a curled profile 78 from
which the exhaust gas is further fed to the outlet side of carburetor throttle plate.
.
Fuel tank 1 provides fuel to the carburetor through a different path 72;
[00026] Figure 4-illustrates the side view of the carburetor 26. Figure 3 shows the
carburetor top 30, throttle lever 32, and throttle adjustment screw 34. During
operation,'the fresh air enters the carburetor from inlet end 31 and leaves the
carburetor from outlet end 33 and further enters the engine inlet. The throttle lever
32 is connected to a throttle plate (described in a more detail in Figure 5). The
throttle lever 32 can be rotated by help of a transmission cable which is further
controlled by the rider by his fist rotation. The screw 34'is calibrated and adjusted to
provide initial default opening of the throttle for regulating adequate amoTJnt of air
entering inside the combustion chamber of the internal combustion engine for
optimized combustion of the fuel.
[00027], Figures 5 illustrates a perspective view of the carburetor 26 with ,
carburetor outlet 33, throttle plate 51, spindle 52, EGR tube 53, and choke 55. The
axes X, Y, Z denote the three virtual axes labelled to elucidate the description of the
current invention. The throttle plate 51 lies on the XY plane and is perpendicular to
the Z aids. The throttle plate 51 doesn’t allow any fuel/air mixture in this condition.
The axis of spindle 52 lies along the X-axis and is capable to rotate either on X-axis
or on an axis parallel to the X—axis. EGR tube‘53 extends till the spindle 52 through
a thorough hole made in the carburetor body. The throttle plate 51 is fastened to the
spindle 52‘ using fasteners. Figure 5 further shows throttle lever portion 55 and
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choke side portion of the carburetor 26. The two ends of spindle 52 of the carburetor
26 are internally supported on throttle lever portion 55 and choke side portion of the
carburetor 26.
[00028] Figures 6 illustrates throttle plate 51, spindle 52, EGR tube 53, spindle
lever side 61, spindle choke side 62, first spindle slot 63 and EGR tube exit end 112
at zero throttle position. As it can be observed from the Figure 6, the throttle plate
51 lies on the XY plane and is perpendicular to the Z axis. The spindle 52 lies along
the X-axis and rotates on an axis parallel to the X—axis. The throttle plate
'51
is
fastened to the spindle 52 using fasteners is also visible. The spindle 52 is capable of
rotating on the X—axis due to which the throttle plate 51 also rotates on the X—axis.
‘ The EGR tube 53 and its end 112 are manufactured with the first spindle slot 63 in
such a way that during zero throttle condition, the EGR tube end 112 of EGR tube
53‘are not aligned and hence no EGR flows from the said EGR tube to the said first
spindle slot 63 during zero throttle condition.
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[00029] Figures 7 illustrates throttle plate 51, spindle 52, EGR tube 53, spindle
lever side 61, spindle choke side 62, first spindle slot 63 and
[EGR
tube exit end 112
during part throttle positions. The EGR tube 53 is disposed with respect to the first
spindle slot 63 in such a way that during part throttle condition for a pre- -determined
range,- the EGR tube end 112 of EGR tube 53 is partly aligned with the first spindle
slot’ 63 hence a regulated amount
of
EGR flows from the said EGR tube 53 to the
said first spindle slot 63 dunng apart throttle condition. Any EGR floWing through
the first spindle slot 63 is capable to corne out of the carburetor through the
carburetor outlet 33 and enter the engine.
[00030] Figures 8-illustrates throttle plate 51, spindle 52, EGR tube 53, spindle
lever side 61, spindle chokels—ide 62, first spindle slot 63 and EGR tube exit end 112
p
at 100% throttle. As illustrated in the drawing, during 100% throttle, the EGR tube
53 with its one end 112 is not aligned with the first spindle slot 63 due to which in
‘case of 100% throttle, the EGR coming in EGR tube 53 can’t pass to the first
spindle slot 62 and hence, during 100% throttle, the EGR connection‘to the engine
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intake is deactivated. Moreover, the interfacing profile and location of EGR tube
outlet end 112 and first spindle slot 62 can be matched together to start- or stop the
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EGR at any pre-determined particular throttle angle.
[00031] Figures 9 illustrates another perspective view of the carburetor 26
showing the carburetor outlet 33, throttle plate 51, spindle 52, EGR tube 53, and
choke 55 as per the second embodiment of the current invention. In this seCond
embodiment of the current invention, the EGR tube 53"is
located on the choke side
of the constant vacuum carburetor 26. The EGR tube 53 has an end 112 which mates
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with the second spindle slot 103 for EGR activation. The second spindle slot 103 is
formed on the choke side of the constant vacuum carburetor 26.
[00032] .Figures 10 illustrate throttle plate 51, spindle‘52, EGR tube 53, second
spindle slot 103 and EGR tube exit end 112 at zero throttle position according to
zero throttle position. In this second embodiment of the current invention, at zero
throttle, as illustrated in the drawing; the EGR tube 53 is not aligned with the second
spindle slot 103 due to which exhaust gas entry to the carburetor outlet 33 portion is
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inhibited.
[00033] Figures 11 illustrates throttle plate 51, spindle 52, EGR tube 53, second
'spindle slot 103 and EGR tube exit end 112 during part throttle position. In the
current position of the throttle plate under part throttle, as illustrated in the drawing;
the EGR tube 53
is
aligned with the second spindle slot 103 due to which a part of
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exhaust gas coming from the EGR tube gets transferred to the said second spindle
slot 103 due to which exhaust gas entry to the carburetor outlet 33 portion is allowed
and a regulated exhaust gas recirculation takes plaCe.
[00034] Figures 12 illustrate throttle plate 51, spindle
5'2, EGR tube_53, second
spindle slot 103 and EGR tube exit end 112 at 100% throttle. In this second
embodiment of the current invention, at full throttle, as illustrated in the drawing;
the EGR tube 53 at
full throttle is not aligned with the second spindle slot 103 due to
which no amount of exhaust gas coming from the EGR tube gets transferred to the
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said second spindle slot 103 and hence, at full throttle exhaust gas recirculationis
inhibited. In addition to the above described embodiments, the interfacing profile
and location of EGR tube outlet end 112 and spindle .slot (63,103) can be optimized
.
andmatched together to start or stop the EGR at any pre-determined throttle angle.
[00035] The carburetor With an internal EGR tube of the current invention as
described herein provides an-EGR entry into engine inlet without major alterations
in the engine which may be a costly approach. The carburetor described herein
further provides a controlled mechanism introduce EGR inside engine to reduce
NOx component from the exhaust gases.