CA1051733A - Exhaust gas recirculation system for ic engines - Google Patents
Exhaust gas recirculation system for ic enginesInfo
- Publication number
- CA1051733A CA1051733A CA257,198A CA257198A CA1051733A CA 1051733 A CA1051733 A CA 1051733A CA 257198 A CA257198 A CA 257198A CA 1051733 A CA1051733 A CA 1051733A
- Authority
- CA
- Canada
- Prior art keywords
- exhaust gas
- throat
- tube
- static pressure
- valve member
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
Landscapes
- Exhaust-Gas Circulating Devices (AREA)
Abstract
Abstract of the Disclosure An exhaust gas recirculation comprises a valve member movable in a venturi tube to restrict the flow of the exhaust gas. The venturi tube and the valve member is sized such that flow velocity of the exhaust gas at the throat of the venturi tube exceeds the sonic velocity when pressure difference between a static pressure at the inlet end of the venturi tube and a static pressure at the outlet end of the venturi tube reaches a value which ranges from 1/2 to 1/4 of a critical pressure which is a static pressure at the throat when flow velocity of the exhaust gas at the throat reaches the sonic velocity.
Description
~L~S~L'733 The present invention relates to exhaust gas recirculation for internal combustion engines and, in particular, to an exhaust gas recirculation valve in a motor vehicle exhaust emission system to provide exhaust gas mass flow rate proportional to effective opening of the valve alone.
One of the methods used to reduce oxides of nitrogen emissions from the exhaust gases in an internal combustion engine is tG recirculate a portion of the exhaust gas- through the engine air intake upstream of the intake manifold. To achieve a greater reduction in the oxides of nitrogen with minimal deterioration of vehicle drivability, the amount of exhaust gas recirculation should be proportional to engine air consumption throughout the normal operating range of the engine.
Conventionally, exhaust gas recirculation is effected by pres~ure difference between exhaust gas pressure and induction vacuum downstream of carburetor throttle valve and the amount o~ exhaust gas recircu~
latlon is controlled by restricting effective cross - ectional area of exhaust gas recirculation passage with exhaust gas recirculation valve in response to venturi vacuum.
This control method involves a problem that the - - ' ' :
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flow rate of exhaust gas recirculation increases as the pressure difference increases even when the opening of the exhaust gas recirculation valve remains constant. This is particularly a problem during low load engine opera-tion, in which the engine induction vacuum is high and format:ion of oxides of nitrogen is little, because the flow rate of exhaust gas recirculation increases excessively.
It is a primary object of the present invention to provide an exhaust gas recirculation which is simple in construction but precisely meter the flow rate of the recircu-lated exhaust gas.
It is another object of the present invention to tailor the design parameters of a valve member and a tube serving as a valve port for the valve member.
Other objects and advantages of the present invention will become apparent from the following description in connec-tion with the accompanying drawings, in which:
Fig. 1 is a schematic view of an exhaust gas recirculation system;
Fig. 2 is an enlarged sectional view of the valve member and the venturi tube serving as the valve port for the valve member; and Fig. 3 which appears on the same sheet of drawings as Fig. 1, is a graph showing the experimental results.
Referring to Fig. 1, there is shown an internal combustion engine 10 having an intake passage 12 in-cluding a carburetor 14 and an exhaust passage 16 through which exhaust gases flow. An exhaust gas recirculation or EGR valve 18 generally comprises a motor housing 20 having a circular diaphragm 22 dividing `the housing into a vacuum chamber 6 and an atmospheric chamber o. A downwardly projecting valve stem 28 is c~ntrally attached to the dia`phragm 22. A valve member 24 is attached to the valve stem 28 and has a conical pintle which cooperates with a venturi tube 26 formed in a valve body 29 to restrict the flow of exhaust gases from a runner 30 formed in the ~alve body 29 of an exhaust gas recirculation or EGR passage to a second 15~ runner 32 formed in the val~e body 29 of the EGR passage.
A coilsd spring 34 disposed in the vacuum chamber 6 serves to normally bias the diaphragm 22, the val~e stem 28, and the valve member 24 to a minimum opening position with respect to the venturi tube 26. :
~uring engine operation, the flow conditions in ..
a venturi 36 of a thro*tls bore 38 of the carburetor 14, produce a vacuum signal proportional to engine air consumption. This vacuum signal is amplified by a suitable apparatus 40 ~nd the amplified signal is used Z5 t~ control the op ening ~ ~o~ing of the v~lvc ~ember ~, ; .
~05:~33 24. This amplified vacuum .signal is applied to the vacuum chamber 24 of the motor housing 20~
Referring to Fig 2, the valve member 24 and the venturi tube 26 which are designed according to the pr.esent invention will be described hereinafter.
The venturi tube 26 has a convergent cone 42 and a divergent cone 44 which are separated at their smallest diameters by a throat 46. An inlet port 48 of the venturi tube 26 fluidly connects with the first runner 30 and from the inlet port 48 the convergent cone 42 leads to the throat 46, while an outlet port 50 o~ the ven~uri tube 26 fluidly connects with the second runner 32 and to the outlet port 50 the divergent cone 44 leads from the throat 46.
t5 The valve member 24 has a conical lower portion 52 having a relatively small cone angle than the divergent cone 44, an upper flange portion 54 adapted to close the outlet port 50 of the venturi tube 26, and a conical intermediate portion 56 between the base of the conical lower portio~ 52 and the upper ~langa portion 54. The conical intermediate portion has a relatively great cone angle than the conical lower portion 52. The valve member 24 is coaxially movable in the venturi tube 26 from a closed position in which the upper flanga portion 54 closes the outlet port 50 .
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of the venturi tube 26 to a maximum opening position, the position illustrated in Fig. 2, in which a smaller diameter portion of the conical lower portion 52 extends into the convergent cone 42 beyond the throat 46 and a larger diameter portion 52 is disposed in the outlet port 50 of the venturi tube 26.
The design parameters for the valve member 24 and the venturi tube 26 are as follows.
Let the effective clearance between the valve member 24 and the throat 46 of the venturi tube 26 when the valve member 24 is in the maximum opening position, the position illustrated i~ Fig. 2, be Ao~ let the effective sectional area at the inlet port 48 of the venturi tube 30 when the valve member 24 is in the ~aximum opening position be A1, and let the effective sectional area between the valve member 24 and the outlet port 50 of the tube 30 when the valve member 24 is in the maximum opening position be A2. Let the . diameter of the throat 46 be D, let the axial length Or the convergent cone 42 be L1 and let the axial length of the divergent cone 44 be L2. Thsn, the valve member 24 and.the tube 30 should satisfy the following relationships.
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D is from 5mm to 20mm.
L1 is from 0.5xD to 2.0xD.
L2 is from 2.0xD to 5.0xD.
A1/Ao is from 2 to 10.
A2/Ao is from 2 to 8.
If the venturi tube 26 and the valve mernber 24 are sized to satisfy these relationships the flow ~elocity of *he exhaust gas at the throat 46 exceeds,t'he s~nic velocity when a pressure difference between a static pressure at the inlet port 4B and a static pressure at the outlet port 50 reaches a value which ranges from ' 1/2 to 1f4 of a critical pressure which is a static pressure at the throat 46 when the flow velocity of the exhaust gas at the throat 46 reaches the sonic velocity.
E,xperimcnt was conducted by the inventors of this invention with a valve member and a venturi tube having'dimensions as follows.
D=10.Omm, LI=8.0mm, L2=30.0mm, AO=25mm2, A1-100mm2 A2=100~m , A1/Ao=5~ A2/Ao=4 As a resul*, the flow velocity,of the exhaust gas at the throat of the tube reaches the sonic velocity when the pressure difference between a static pressure at ~n ~inlet port of the tube and a static pressure at an outlet port of the venturi tube reaches 110mmHg which ,"25 is 30% of the cr1tical pressure of 360mmHg.The flow , '. ' : . ':
,~ ~
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velocity of the exhaust gas at the throat remains the sonic velocity even if the pressure difference increases up to 400mmHg.
Fig. 3 shows characteristic curves (shown in solid lines~ when the valve member is lifted from the closed position of the valYe member by 6mm and 10mm, respectively, showing the experimental results obtained by th~ expe~iment. :
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.
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One of the methods used to reduce oxides of nitrogen emissions from the exhaust gases in an internal combustion engine is tG recirculate a portion of the exhaust gas- through the engine air intake upstream of the intake manifold. To achieve a greater reduction in the oxides of nitrogen with minimal deterioration of vehicle drivability, the amount of exhaust gas recirculation should be proportional to engine air consumption throughout the normal operating range of the engine.
Conventionally, exhaust gas recirculation is effected by pres~ure difference between exhaust gas pressure and induction vacuum downstream of carburetor throttle valve and the amount o~ exhaust gas recircu~
latlon is controlled by restricting effective cross - ectional area of exhaust gas recirculation passage with exhaust gas recirculation valve in response to venturi vacuum.
This control method involves a problem that the - - ' ' :
' ........... ..
~ ~ . , , . .
.~ . .
' ~ ~
. ,.
iL~5~73~
flow rate of exhaust gas recirculation increases as the pressure difference increases even when the opening of the exhaust gas recirculation valve remains constant. This is particularly a problem during low load engine opera-tion, in which the engine induction vacuum is high and format:ion of oxides of nitrogen is little, because the flow rate of exhaust gas recirculation increases excessively.
It is a primary object of the present invention to provide an exhaust gas recirculation which is simple in construction but precisely meter the flow rate of the recircu-lated exhaust gas.
It is another object of the present invention to tailor the design parameters of a valve member and a tube serving as a valve port for the valve member.
Other objects and advantages of the present invention will become apparent from the following description in connec-tion with the accompanying drawings, in which:
Fig. 1 is a schematic view of an exhaust gas recirculation system;
Fig. 2 is an enlarged sectional view of the valve member and the venturi tube serving as the valve port for the valve member; and Fig. 3 which appears on the same sheet of drawings as Fig. 1, is a graph showing the experimental results.
Referring to Fig. 1, there is shown an internal combustion engine 10 having an intake passage 12 in-cluding a carburetor 14 and an exhaust passage 16 through which exhaust gases flow. An exhaust gas recirculation or EGR valve 18 generally comprises a motor housing 20 having a circular diaphragm 22 dividing `the housing into a vacuum chamber 6 and an atmospheric chamber o. A downwardly projecting valve stem 28 is c~ntrally attached to the dia`phragm 22. A valve member 24 is attached to the valve stem 28 and has a conical pintle which cooperates with a venturi tube 26 formed in a valve body 29 to restrict the flow of exhaust gases from a runner 30 formed in the ~alve body 29 of an exhaust gas recirculation or EGR passage to a second 15~ runner 32 formed in the val~e body 29 of the EGR passage.
A coilsd spring 34 disposed in the vacuum chamber 6 serves to normally bias the diaphragm 22, the val~e stem 28, and the valve member 24 to a minimum opening position with respect to the venturi tube 26. :
~uring engine operation, the flow conditions in ..
a venturi 36 of a thro*tls bore 38 of the carburetor 14, produce a vacuum signal proportional to engine air consumption. This vacuum signal is amplified by a suitable apparatus 40 ~nd the amplified signal is used Z5 t~ control the op ening ~ ~o~ing of the v~lvc ~ember ~, ; .
~05:~33 24. This amplified vacuum .signal is applied to the vacuum chamber 24 of the motor housing 20~
Referring to Fig 2, the valve member 24 and the venturi tube 26 which are designed according to the pr.esent invention will be described hereinafter.
The venturi tube 26 has a convergent cone 42 and a divergent cone 44 which are separated at their smallest diameters by a throat 46. An inlet port 48 of the venturi tube 26 fluidly connects with the first runner 30 and from the inlet port 48 the convergent cone 42 leads to the throat 46, while an outlet port 50 o~ the ven~uri tube 26 fluidly connects with the second runner 32 and to the outlet port 50 the divergent cone 44 leads from the throat 46.
t5 The valve member 24 has a conical lower portion 52 having a relatively small cone angle than the divergent cone 44, an upper flange portion 54 adapted to close the outlet port 50 of the venturi tube 26, and a conical intermediate portion 56 between the base of the conical lower portio~ 52 and the upper ~langa portion 54. The conical intermediate portion has a relatively great cone angle than the conical lower portion 52. The valve member 24 is coaxially movable in the venturi tube 26 from a closed position in which the upper flanga portion 54 closes the outlet port 50 .
- ~
' .. .' : ' . .
" ' : ,: ' . ' .
., ~
~5~73~
of the venturi tube 26 to a maximum opening position, the position illustrated in Fig. 2, in which a smaller diameter portion of the conical lower portion 52 extends into the convergent cone 42 beyond the throat 46 and a larger diameter portion 52 is disposed in the outlet port 50 of the venturi tube 26.
The design parameters for the valve member 24 and the venturi tube 26 are as follows.
Let the effective clearance between the valve member 24 and the throat 46 of the venturi tube 26 when the valve member 24 is in the maximum opening position, the position illustrated i~ Fig. 2, be Ao~ let the effective sectional area at the inlet port 48 of the venturi tube 30 when the valve member 24 is in the ~aximum opening position be A1, and let the effective sectional area between the valve member 24 and the outlet port 50 of the tube 30 when the valve member 24 is in the maximum opening position be A2. Let the . diameter of the throat 46 be D, let the axial length Or the convergent cone 42 be L1 and let the axial length of the divergent cone 44 be L2. Thsn, the valve member 24 and.the tube 30 should satisfy the following relationships.
, , ' ' ' '' ~, _ 6 - :
' ..
-~ " .
'' " , .
.
,, . . ,, , . , ., , ~
~15~73;~
D is from 5mm to 20mm.
L1 is from 0.5xD to 2.0xD.
L2 is from 2.0xD to 5.0xD.
A1/Ao is from 2 to 10.
A2/Ao is from 2 to 8.
If the venturi tube 26 and the valve mernber 24 are sized to satisfy these relationships the flow ~elocity of *he exhaust gas at the throat 46 exceeds,t'he s~nic velocity when a pressure difference between a static pressure at the inlet port 4B and a static pressure at the outlet port 50 reaches a value which ranges from ' 1/2 to 1f4 of a critical pressure which is a static pressure at the throat 46 when the flow velocity of the exhaust gas at the throat 46 reaches the sonic velocity.
E,xperimcnt was conducted by the inventors of this invention with a valve member and a venturi tube having'dimensions as follows.
D=10.Omm, LI=8.0mm, L2=30.0mm, AO=25mm2, A1-100mm2 A2=100~m , A1/Ao=5~ A2/Ao=4 As a resul*, the flow velocity,of the exhaust gas at the throat of the tube reaches the sonic velocity when the pressure difference between a static pressure at ~n ~inlet port of the tube and a static pressure at an outlet port of the venturi tube reaches 110mmHg which ,"25 is 30% of the cr1tical pressure of 360mmHg.The flow , '. ' : . ':
,~ ~
- .
,' : ~,' S~3~
velocity of the exhaust gas at the throat remains the sonic velocity even if the pressure difference increases up to 400mmHg.
Fig. 3 shows characteristic curves (shown in solid lines~ when the valve member is lifted from the closed position of the valYe member by 6mm and 10mm, respectively, showing the experimental results obtained by th~ expe~iment. :
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.
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Claims
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
In an exhaust gas recirculation for an internal combustion engine having an intake passage and an exhaust passage:
a tube having an inlet end fluidly connected with the exhaust passage and an outlet end fluidly connected with the intake passage, said tube having a convergent cone leading from the inlet end and a divergent cone leading to the outlet end, the diver-gent and convergent cones being separated at their smallest diameters by a throat;
a valve member movable is said tube between a maximum opening and a minimum opening with respect to said tube to restrict flow of exhaust gas therethrough;
said tube and said valve member being sized such that flow velocity of the exhaust gas at the throat exceeds the sonic velocity when pressure dif-ference between a static pressure at the inlet end and a static pressure at the outlet end reaches a value which ranges from 1/2 to 1/4 of a critical static pressure at the throat which is a static pressure at the throat when flow velocity of the exhaust gas at the throat reaches the sonic velocity.
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
In an exhaust gas recirculation for an internal combustion engine having an intake passage and an exhaust passage:
a tube having an inlet end fluidly connected with the exhaust passage and an outlet end fluidly connected with the intake passage, said tube having a convergent cone leading from the inlet end and a divergent cone leading to the outlet end, the diver-gent and convergent cones being separated at their smallest diameters by a throat;
a valve member movable is said tube between a maximum opening and a minimum opening with respect to said tube to restrict flow of exhaust gas therethrough;
said tube and said valve member being sized such that flow velocity of the exhaust gas at the throat exceeds the sonic velocity when pressure dif-ference between a static pressure at the inlet end and a static pressure at the outlet end reaches a value which ranges from 1/2 to 1/4 of a critical static pressure at the throat which is a static pressure at the throat when flow velocity of the exhaust gas at the throat reaches the sonic velocity.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP50094706A JPS5218530A (en) | 1975-08-05 | 1975-08-05 | Exhaust gas reflux control system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1051733A true CA1051733A (en) | 1979-04-03 |
Family
ID=14117596
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA257,198A Expired CA1051733A (en) | 1975-08-05 | 1976-07-16 | Exhaust gas recirculation system for ic engines |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS5218530A (en) |
| CA (1) | CA1051733A (en) |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS51114524A (en) * | 1975-03-31 | 1976-10-08 | Nissan Motor Co Ltd | Exhaust recycling controlling device |
-
1975
- 1975-08-05 JP JP50094706A patent/JPS5218530A/en active Pending
-
1976
- 1976-07-16 CA CA257,198A patent/CA1051733A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5218530A (en) | 1977-02-12 |
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