JPH10281012A - Axial static mixer for spark ignition engines. - Google Patents

Abstract

(57) [Problem] To provide an axial flow static mixer that makes the concentration of air-fuel mixture uniform, eliminates variations in exhaust temperature, improves combustion efficiency, and enables complete exhaust gas treatment by a three-way catalyst device. provide. SOLUTION: A cylindrical bypass flow introduction pipe 2 whose front end is closed by a blind cover 3 and into which a bypass air A 'flows into a base end is placed in a mixture passage 26 through which a mixture M of air and fuel flows. Place them in parallel. A number of blowout holes 4 are formed in the peripheral wall of the pipe 2, and a spiral vortex generating blade 5 is fixed to the outer periphery of the pipe 2 so as to swirl the air-fuel mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of mixing air and fuel in a mixer, and mixing air or gaseous fuel bypassing the mixer with the mixture to control the air-fuel ratio and supply the mixture to a cylinder. The present invention relates to an axial static mixer of a spark ignition engine.

[0002]

2. Description of the Related Art Conventionally, an air bypass type mixer is used in a spark ignition gas engine as shown in FIG. This engine 19 is provided with CO, HC,
In order to remove NOx, a three-way catalyst device 23 is provided in the exhaust pipe 20 to oxidize oxidizing components (CO ₂ , H ₂ O) and reducing components (CO, HC, H ₂ ) in the exhaust gas. In order to simultaneously treat the three components while maintaining theoretically equivalent conditions, the air-fuel ratio is controlled to a very narrow range near the stoichiometric air-fuel ratio. Therefore, a mixer 13 that mixes air and fuel gas at a predetermined ratio into an air supply system of the engine 19 to form an air-fuel mixture,
A bypass pipe 14 that connects the upstream air pipe 11 and the downstream mixed pipe 15 to partially bypass the air supply, and a flow rate interposed in the bypass pipe 14, the opening of which is adjusted by an actuator 17. A control valve 16 and an electronic governor 1 interposed in the air-fuel mixture pipe 15 for adjusting the flow rate of the air-fuel mixture according to the load.
8 and the exhaust pipe 20 is connected to the conventional three-way catalyst device 2.
3, an oxygen concentration sensor 21 is provided only on the upstream side of the microcontroller 24 based on the detection signal of the sensor 21.
By operating the actuator 17 to adjust the bypass air amount to approximately 5% of the required total air amount, a single oxygen concentration sensor system that performs feedback control so that the air-fuel ratio becomes the stoichiometric air-fuel ratio is adopted. I was

[0003] However, this single oxygen concentration sensor system can satisfactorily purify exhaust gas at the beginning of operation,
As the three-way catalyst device 23 is used for a long time, it becomes clear that the air-fuel ratio to be targeted for obtaining the highest purification rate shifts to a fuel-rich side from the stoichiometric air-fuel ratio, and the amount of bypass air is reduced. At the time of adjustment, it is necessary to reset the target air-fuel ratio to the shifted air-fuel ratio. Therefore, an auxiliary oxygen concentration sensor 22 shown in FIG. 4 is also provided in the exhaust pipe on the downstream side of the three-way catalyst device 23, and the microcontroller 24 operates based on both the detection signals of the oxygen concentration sensor 21 and the auxiliary oxygen concentration sensor 22. Thus, a double oxygen concentration sensor system that controls the air-fuel ratio of the air-fuel mixture supplied to the engine 19 to a shifted air-fuel ratio by controlling the amount of bypass air is employed.

This double oxygen concentration sensor system is an advanced exhaust gas purification technology developed for automobiles, and the detection signal output from the oxygen concentration sensor 21 in this system is, as shown in FIG. A waveform of a cycle T that increases and decreases according to the concentration of oxygen is drawn. In order to maximize the purifying performance of the three-way catalyst device 23, the period T of the waveform of the detection signal is made sufficiently short, and the average value of the air-fuel ratio of the supply air-fuel mixture is set to approximately the stoichiometric air-fuel ratio. It is known that it is necessary. That is, since it is necessary to control the air-fuel ratio of the supplied air-fuel mixture with high accuracy while frequently opening and closing the flow control valve 16, the amount of air flowing through the bypass pipe 14 must be increased. In the case of a single oxygen concentration sensor system, the required air amount is approximately 10%, which is twice the required total air amount, which is 5%.

[0005]

As described above, in the gas engine, it is necessary to control the air-fuel ratio within a very narrow range near the stoichiometric air-fuel ratio. It must be a uniform concentration substantially equal to the stoichiometric air-fuel ratio as far as possible. Therefore, the gas engine of the conventional single oxygen concentration sensor system
As shown in the detailed view of FIG. 5, on the inlet side of the mixer 13, the air A from the air pipe 11 and the fuel gas G from the fuel pipe 12 are mixed to form an air-fuel mixture M. The bypass air A ′ from the bypass pipe 14 joins at a junction J corresponding to J in FIG. 4 to become a mixture M ′ having a stoichiometric air-fuel ratio,
After flowing through the approaching section L which forms a part of the mixture passage 26 provided to promote the uniformity of the mixture M ′, the mixture flows out to the mixture pipe 15 via the throttle valve 25. However, in the gas engine of the latest double oxygen concentration sensor system, the amount of bypass air joining from the bypass pipe 14 is twice as large as that of the single oxygen concentration system as described above. In the structure of FIG. 5 in which the air-fuel mixture is simply joined, it is difficult to obtain a mixture having a uniform concentration.
If mixing takes time and turbulence is created over a wide range of lengths, the design requirements will not be met due to engine space. That is, by-pass air A 'to be mixed with the air-fuel mixture M flows in a laminar flow state as much as possible, whereby stable mixing is not performed, and it is possible to obtain an air-fuel mixture having a uniform concentration substantially equal to the stoichiometric air-fuel ratio. It is difficult.

As described above, it is difficult to obtain an air-fuel mixture having a uniform concentration in the above-described conventional bypass system of a spark ignition engine, so that the concentration of the air-fuel mixture supplied to the combustion chamber of each cylinder becomes uneven. There is a problem that the exhaust temperature of each cylinder varies and the combustion efficiency deteriorates. In addition, since the air-fuel ratio in each cylinder deviates from the stoichiometric air-fuel ratio, the function of the three-way catalyst device 23 cannot be sufficiently exhibited, and there is a problem that exhaust gas processing is incomplete.

[0007] Therefore, an object of the present invention is to make the air or gaseous fuel which has been bypassed join the air-fuel mixture so as to have a concentration as uniform as possible.
An axial flow static mixer for a spark ignition engine that can improve combustion efficiency by eliminating variations in exhaust gas temperature, maintain the air-fuel ratio at approximately the stoichiometric air-fuel ratio without concentration, and enable complete treatment of exhaust gas by a three-way catalytic converter To provide.

[0008]

In order to achieve the above object, an axial static mixer of a spark ignition engine according to the present invention mixes air and fuel in a mixer, and the air-fuel mixture is bypassed by the mixer. Alternatively, the gaseous fuel is merged in the axial flow direction to control the air-fuel ratio and supplied to the cylinder, and the mixture is disposed in a mixture passage in which the mixture flows, in parallel to the flow direction, and the tip is closed. A bypass flow introduction pipe into which the air or gaseous fuel to be bypassed flows into the base end, a plurality of blowout holes provided through the peripheral wall of the bypass flow introduction pipe, and an outer periphery of the bypass flow introduction pipe, A swirl generating blade fixed to swirl the air-fuel mixture is provided.

[0009]

In the axial flow static mixer, a bypass flow introduction pipe having a closed end in the flow direction in the mixture passage, a plurality of blowout holes formed in the peripheral wall, and a vortex generating blade on the outer periphery is arranged. Have been. Now, it is assumed that bypass air that has bypassed the mixer flows into the base end of the bypass flow introduction pipe. Then, when the mixture of air and fuel mixed in the mixer passes through the mixture passage narrowed by the bypass flow introduction pipe, the flow velocity increases and the pressure decreases. The bypass air that has flowed in into the air-fuel mixture passage from the plurality of outlet holes with the suction effect by the above-described decompression is added,
The air-fuel mixture is mixed well with the air-fuel mixture to dilute the air-fuel mixture, and a vortex-generating blade on the outer periphery of the pipe forms a vortex-shaped swirling flow. And supplied to the engine cylinder. When the fuel gas bypassing the mixer flows into the base end of the bypass flow introduction pipe, the fuel gas mixes with the air-fuel mixture instead of the above-described bypass air. Energy will be supplied to the engine.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. FIG. 1 is a schematic plan view showing one embodiment of a mixer provided with an axial static mixer of the present invention. The axial static mixer 1 includes an air pipe 11 and a fuel pipe 1.
5 and the bypass pipe 14 in the spark-ignition gas engine of FIGS. 4 and 5 in the mixture path 26 between the mixer 13 and the throttle valve 25 as described in FIG.
Are provided in parallel with the flow direction at a position corresponding to the junction J. The axial flow static mixer 1 is shown in FIG.
As shown in the partially cutaway side and front views of (A) and (B), the tip is closed by a blind plate 3 and a number of blowout holes 4 are formed in the peripheral wall.
And is fixed to an elbow-shaped tip of a bypass pipe 14 which is mounted orthogonally to the conduit of the air-fuel mixture passage 26 and has a bypass flow introduction pipe 2 provided with a spiral vortex generating blade 5 on the outer periphery. .

As shown in the partial vertical and horizontal sectional views of FIGS. 2C and 2D, the boss 8 is fixed to the center of the elbow-shaped tip of the bypass pipe 14 via three arms 9. 3A and 3B, which are vertical and horizontal detailed sectional views of the axial flow static mixer 1, the base flange 7 of the bypass flow introduction pipe 2 is attached to the above-mentioned elbow-shaped tip. At the same time, the shaft portion of the bolt 6 (see FIG. 2A) is inserted into the center hole 10 of the blind plate 3 at the tip of the pipe 2, and the tip is screwed into the female screw hole of the boss 8. Done. The vortex generation blade 5 cuts a ring made of a steel plate or the like having an inner diameter and a predetermined outer diameter that is 5% larger than the outer diameter of the bypass flow introduction pipe 2 at one location in the radial direction, and helically cuts the ring. Is formed by welding a required number of strips to the outer periphery of a bypass flow introducing pipe 2 made of a steel plate. The bypass flow introduction pipe 2 having the large number of through holes 4 can be made by processing punching metal.

The axial static mixer of the spark ignition engine having the above configuration operates as follows. Mixer 1 of FIG.
The mixture of the air A and the fuel gas G mixed on the inlet side of the fuel cell 3 flows through the mixture passage 26 as shown by the arrow M. The mixture passage 26 is provided with a flow control valve 1 provided orthogonally thereto.
The above-mentioned passage 2 is provided in the elbow at the tip of the bypass pipe 14 having
Since the flow path is narrowed by the bypass flow introduction pipe 2 of the static mixer 1 fixed in six directions, the flow rate of the air-fuel mixture M passing therethrough increases, and the pressure decreases. On the other hand, in the bypass flow introduction pipe 2 (see FIG. 2),
Although the bypass air flows through the bypass pipe 14, the suction effect due to the decrease in the pressure of the outer mixture passage 26 is added to the outside air passage 26, so that the air is blown out vigorously into the mixture passage 26 from the large number of blowout holes 4 and mixed well with the mixture M. Together with this, it is further diluted, and as it flows further downstream of the passage, a spiral swirling flow is formed by the spiral vortex generating blades 5 on the outer circumference of the pipe 2. Is further promoted, and becomes an ideal diluted air-fuel mixture M ′ having a uniform concentration without shading, and is supplied to the cylinder of the engine through the air-mixing pipe 15.

As described above, according to the axial-flow static mixer 1 of the embodiment, the air-fuel mixture M and the bypass air A 'are sufficiently mixed to form an ideal mixture having a uniform concentration without density. Since M 'can be supplied to each cylinder of the engine, the exhaust temperature of each cylinder does not vary, and the combustion efficiency is improved. Also, since the air-fuel ratio of the air-fuel mixture supplied to each cylinder can be accurately controlled within a narrow range near the stoichiometric air-fuel ratio, the function of the three-way catalyst device provided in the exhaust system can be fully exhibited, and Complete processing of the gas becomes possible.

In the above embodiment, the mixer of the air bypass system has been described. However, the static mixer of the present invention can be applied to a system in which a fuel gas is bypassed instead of air. Therefore, the ideal enriched mixture having a uniform concentration is supplied to the engine.

[0015]

As is apparent from the above description, the static mixer of the spark ignition engine according to the present invention mixes air and fuel in the mixer, and forms an air or gaseous mixture in which the mixture is bypassed by the mixer. The fuel is merged to perform air-fuel ratio control and supplied to a cylinder, which is arranged in a mixture passage in which the mixture flows, in which a front end is closed, and a bypass is provided at a base end. A bypass flow introduction pipe through which air or gaseous fuel flows,
Since a plurality of blow-out holes penetrating through the peripheral wall of the bypass flow introduction pipe and a vortex generating blade fixed to swirl the air-fuel mixture on the outer periphery of the bypass flow introduction pipe are provided, air and fuel By thoroughly mixing the air-fuel mixture with bypass air or gaseous fuel, it is possible to supply an ideal air-fuel mixture having a uniform concentration without concentration to each cylinder of the engine, and the exhaust temperature of each cylinder varies. And the combustion efficiency is improved. Further, since the air-fuel ratio of the air-fuel mixture supplied to each cylinder can be accurately controlled within a narrow range near the stoichiometric air-fuel ratio, the function of the three-way catalyst device provided in the exhaust system can be sufficiently exhibited. In addition, an ideal air-fuel mixture can be provided even in the lean-fuel type air-fuel ratio control, and exhaust gas can be completely processed.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing an embodiment of a mixer provided with an axial static mixer of the present invention.

FIG. 2 is a partially cutaway side view, a front view, a partial longitudinal sectional view, and a partial transverse sectional view of the axial flow static mixer.

FIG. 3 is a vertical and horizontal detailed sectional view of the axial flow static mixer.

FIG. 4 is a diagram showing an air bypass type spark ignition gas engine supply / exhaust system including a conventional mixer.

FIG. 5 is a plan view showing the conventional mixer.

6 is a diagram showing a detection signal of the oxygen concentration sensor of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Axial static mixer, 2 ... Bypass flow introduction pipe, 3 ... Blind lid, 4 ... Blowhole, 5 ... Vortex generating blade, 6 ... Bolt, 7 ... Flange, 8 ... Boss, 11 ... Air pipe, 12 ... Fuel Pipe, 13: mixer, 14: bypass pipe, 15: mixture pipe, 25 ... throttle valve, 26: mixture path, A ...
Air, G: fuel gas, M: mixture, A ': bypass air, M': dilution mixture, J: junction.

Claims (1)

[Claims] 1. An air and fuel are mixed in a mixer, and the air or gaseous fuel bypassing the mixer is merged with the air / fuel mixture in an axial flow direction to control an air / fuel ratio and supply the air / cylinder to a cylinder. An axial flow static mixer for a spark ignition engine, wherein the air or gaseous fuel is disposed in a mixture passage in which the mixture flows, in a direction parallel to the flow direction, the tip is closed, and the bypassed air or gaseous fuel flows into a base end. A bypass flow introducing pipe, a plurality of blowout holes penetrating through a peripheral wall of the bypass flow introducing pipe, and a vortex generating blade fixed around the bypass flow introducing pipe so as to swirl the air-fuel mixture. An axial flow static mixer for a spark ignition engine.