KR102125283B1 - Exhaust structure for diesel engine - Google Patents

Abstract

The present invention relates to an exhaust structure for a diesel engine, including an exhaust pipe formed to allow a flow of exhaust gas and installed with a urea water injection module; and a flow rate control unit provided to control the flow rate of the exhaust gas flowing into the exhaust pipe. The exhaust structure for a diesel engine increases mixing efficiency of urea water by increasing the flow rate of the exhaust gas by reducing the area of a flow path through which the exhaust gas flows by closing a valve plate when the exhaust flow rate is small.

Description

Exhaust structure for diesel engines {EXHAUST STRUCTURE FOR DIESEL ENGINE}

The present invention relates to an exhaust structure for a diesel engine, and more particularly, to an exhaust structure for a diesel engine through which exhaust gas is passed and mixed with urea water.

The engine has a slight sequence difference depending on whether it is a four-stroke or two-stroke engine, but it repeatedly performs suction, compression, explosion, and exhaust operations and generates power.

During operation of the engine, fuel injected into the cylinder of the engine together with air is discharged through exhaust manifolds out of each cylinder in the exhaust stroke, and the exhaust manifolds are connected to a single exhaust pipe and transferred to the muffler at the rear of the vehicle. It is configured to be discharged.

However, such exhaust gas is not directly discharged through the exhaust structure, but is recirculated into the engine through an exhaust gas recirculation (EGR) device, a fuel evaporation gas control device, etc. in order to suppress emission of pollutants. And it is transferred to the muffler via a catalyst device or the like.

At this time, the conventional exhaust structure for a diesel engine is simply provided in the form of a pipe so that the exhaust gas flows.

In particular, even in the case of an SCR system (selective catalyst reduction) in which urea water injection module is provided to reduce NOX by mixing urea water with exhaust gas, exhaust gas flows through the exhaust pipe regardless of the exhaust flow rate.

However, in the case of the SCR system, when the flow rate of the exhaust gas is slow, the performance that the urea water injected from the urea water injection module is mixed with the exhaust gas is lowered, resulting in a problem that the suppression efficiency of pollutants decreases.

That is, since the flow rate of exhaust gas is high in the high load region of the engine as in the high-speed driving in the SCR system, the number of urea injected from the urea water injection module is well mixed to effectively reduce pollutants, while the displacement in the low load region of the engine There is a problem that the urea water is not well mixed due to the low and low exhaust gas flow rate.

5 shows the ratio distribution of NOx according to urea water spray in the low load state and the high load state.

FIG. 5(a) is a spray uniformity (upper side) and a distribution table of NOx (lower side) in a low load state, where the number of urea is not uniformly mixed, and thus a region having a small NOx (blue region on the lower side distribution table) and many regions (red) Area).

In contrast, FIG. 5(b) shows the spray uniformity (upper side) and NOx distribution table (lower side) in a high load state, and the exhaust flow rate and the unit exhaust flow rate increase, whereby the urea water is sprayed relatively evenly, resulting in a high NOx concentration ( It can be seen that there are few regions).

Therefore, it is necessary to develop a technique for efficiently mixing urea water by increasing the flow rate of exhaust gas even in the low-load region of the engine.

Korean Patent Publication No. 10-2011-0021454 (2011.03.04)

The present invention was created to improve the problems of the conventional exhaust structure for a diesel engine as described above, and provides an exhaust structure for a diesel engine that improves the mixing efficiency of urea water by increasing the flow rate of exhaust gas even when the exhaust flow rate is small. It has a purpose.

In order to achieve the above object, the exhaust structure for a diesel engine according to the present invention is formed to flow the exhaust gas and is provided to control the flow rate of the exhaust gas flowing into the exhaust pipe, and the exhaust pipe installed with the urea water injection module. It characterized in that it comprises a flow rate control unit.

At this time, the flow rate control unit may include an exhaust adapter provided to be coupled to the exhaust pipe, and a valve plate provided in the exhaust adapter and opened and closed to adjust a cross-sectional area of a flow path flowing into the exhaust pipe.

In addition, the flow rate control unit is installed in the exhaust pipe, it is provided to flow the exhaust gas therein, it is possible to further include a variable pipe formed to have an outer diameter smaller than the inner diameter of the exhaust pipe.

On the other hand, the valve plate includes a plate body provided to be opened and closed by hydraulic pressure of the exhaust gas, and a torsion spring formed to apply a restoring force to the plate body by fixing one side to the exhaust adapter and combining the plate body and the other side. It is also possible to do.

On the other hand, the variable pipe may include a pipe body provided with an exhaust gas flowing therein, and a stopper formed on an outer circumferential surface of the pipe body and protruding to support the valve plate when the valve plate is closed. .

At this time, the variable pipe is formed extending from the outer peripheral surface of the pipe body, it is also possible to further include a pipe fixing portion provided to be coupled to the inner peripheral surface of the exhaust pipe.

On the other hand, the urea water injection module may be arranged corresponding to the position of the end portion in the direction in which the exhaust gas of the variable pipe is discharged.

As described above, according to the exhaust structure for a diesel engine according to the present invention, when the flow rate is low, the valve plate is closed to decrease the area of the flow path through which the exhaust gas flows, thereby increasing the flow rate of the exhaust gas to increase the mixing efficiency of urea water It works.

1 is a cross-sectional view when the valve plate is closed in the exhaust structure for a diesel engine according to an embodiment of the present invention,
Figure 2 is a cross-sectional view in a direction perpendicular to Figure 1,
Figure 3 is a cross-sectional view when the valve plate is opened in the exhaust structure for a diesel engine according to an embodiment of the present invention,
Figure 4 is a cross-sectional view in the direction perpendicular to Figure 3,
5 is a graph showing the ratio distribution of NOx according to urea water spray in a low load state and a high load state.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 to 4, the exhaust structure for a diesel engine according to an embodiment of the present invention includes an exhaust pipe 100 and a flow rate control unit 200, and the flow rate control unit 200 is an exhaust adapter 210 , A valve plate 220 and a variable pipe 230.

The exhaust pipe 100 is formed in the form of a hollow pipe so that exhaust gas flows therein, and is inserted into and coupled to the exhaust adapter 210, and the variable pipe 230 is inside the exhaust pipe 100. Is inserted and fixedly coupled.

In addition, an urea water injection module 10 is fastened to the outer circumferential surface of the exhaust pipe 100, and the urea water is ejected from the urea water injection module 10 so that the urea can be discharged into the tube of the exhaust pipe 100. It is provided to communicate with the injection port of the male injection module (10).

The exhaust adapter 210 is provided on the exhaust passage of a square vehicle engine (not shown), the exhaust pipe 100 is provided to be inserted, and includes a pipe inserting part 211 and a plate opening and closing part 212. .

That is, the exhaust adapter 210 is formed in a pipe shape, the plate opening and closing portion 212 is formed in a polygonal hole shape, the pipe inserting portion 211 is formed in the form of a circular hole, the plate opening and closing portion 212 and the pipe insertion portion 211 is formed to communicate with each other.

Meanwhile, in the present embodiment, the exhaust adapter 210 is formed in a shape similar to a hollow square pillar, and the plate opening and closing portion 212 is formed in a square hole shape, but is not limited thereto.

At this time, a plurality of the valve plate 220 is coupled to the side wall surface of the plate opening and closing portion 212, the exhaust pipe 100 is inserted and coupled to the pipe insertion portion 211, the variable pipe 230 is The plate opening and closing portion 212 and the pipe insertion portion 211 are accommodated.

The valve plate 220 is provided in plurality and is coupled to the side wall surface of the plate opening and closing portion 212 of the exhaust adapter 210, and includes a plate body 221 and a torsion spring 222.

At this time, the plate body 221 is coupled to the torsion spring 222 is provided to be capable of pivoting the torsion spring 222, a flat plate to block the plate opening and closing portion 212 through which the exhaust gas flows It is formed in a shape, it is formed in a size that can contact the outer peripheral surface of the variable pipe (230).

That is, the plate main body 221 is formed in a shape similar to a trapezoidal plate with one side contacting the exhaust adapter 210, and a side facing the side contacting the exhaust adapter 210 has an outer circumferential surface of the variable pipe 230. It is formed in a concave arc shape corresponding to the curvature. Therefore, when a plurality of the plate body 221 is closed (when blocking the exhaust adapter 210), a space between a side wall surface of the plate opening and closing portion 212 and an outer circumferential surface of the variable pipe 230 is blocked.

On the other hand, in this embodiment, the plate body 221 is composed of four, but is not limited thereto, and may be changed in correspondence with the internal structure of the exhaust adapter 210.

The torsional spring 222 has one end fixedly coupled to the sidewall surface of the plate opening and closing portion 212, and the other end fixedly coupled to the plate body 221. At this time, in this embodiment, the initial position of the torsional spring 222 is set to a state in which the plate body 221 blocks the space between the side wall surface of the plate opening and closing portion 212 and the outer peripheral surface of the variable pipe 230. The plate body 221 is provided to be rotatable about the coil of the torsion spring 222 by the hydraulic pressure (flow velocity) of the exhaust gas.

The variable pipe 230 is provided to penetrate the exhaust adapter 21, is inserted into the exhaust pipe 100, is coupled to the inner peripheral surface of the exhaust pipe 100, the pipe body 231, stopper 232 and a pipe fixing portion 233.

The pipe body 231 is formed in a pipe shape to be accommodated inside the exhaust adapter 210 and the exhaust pipe 100, and is formed to have an outer diameter smaller than the inner diameter of the exhaust pipe 100. At this time, the pipe body 231 is axial one end is accommodated in the interior of the variable pipe 230, the urea water injection module 10 is provided corresponding to one end of the pipe body 231. That is, the urea water injection module 10 is disposed at a predetermined interval along an axial direction from one end of the pipe body 231.

The stopper 232 is formed to protrude along the circumferential direction on the outer circumferential surface of the pipe body 231, and is provided to be in contact with the plate body 221. Therefore, when the plate body 221 is closed, the plate body 221 is in contact with the stopper 232, and the plate body 221 is caught in the stopper 232 and opened in a direction in which exhaust gas flows in. Prevent things.

The pipe fixing part 233 is formed to extend radially outward from the outer circumferential surface of the pipe body 231 and is coupled to the inner circumferential surface of the exhaust pipe 100. Meanwhile, in the present embodiment, two pipe fixing parts 233 are formed along the axial direction, and are fixedly coupled to the exhaust pipe 100 by welding, but are not limited thereto.

With reference to Figures 1 to 4 to describe the operation and effects of the exhaust structure for a diesel engine according to an embodiment of the present invention will be described by dividing the low load state and the high load state.

First, in a low load state in which the flow rate of the exhaust gas is low, the flow rate and hydraulic pressure of the exhaust gas flowing into the exhaust adapter 210 are relatively low. At this time, since the exhaust structure for a diesel engine of the present invention is set so that the plate body 221 closes the plate opening and closing portion 212 to an initial position, the torsional spring 222 exhausts the plate body 221. Elastic force is applied to rotate toward the inflow direction. On the other hand, the plate body 221 is limited to open in the direction in which the exhaust gas is introduced by the stopper 232.

Therefore, under the flow velocity (hydraulic) of the exhaust gas smaller than a predetermined flow velocity (hydraulic), the elastic force of the torsion spring 222 cannot be overcome, and all the exhaust gas flows into the variable pipe 230.

In this case, the cross-sectional area of the flow passage through the exhaust gas flowing into the variable pipe 230 is reduced, and the flow rate of the exhaust gas in the variable pipe 230 is increased (continuous equation, equation of continuity). As a result, the exhaust gas having an increased speed passing through the variable pipe 230 increases the efficiency of mixing with the urea water injected from the urea water injection module 10.

On the other hand, in a high load state in which the flow rate of the exhaust gas is high, the flow rate and hydraulic pressure of the exhaust gas flowing into the exhaust adapter 210 are relatively high. Therefore, the plate body 221, which was supported by the stopper 232 and the torsion spring 222, of the torsion spring 222 when an exhaust gas higher than a predetermined flow rate (hydraulic) flows in. Overcome the elastic force and rotate the plate body 221 in the direction of the exhaust pipe 100 (the direction in which the exhaust gas is discharged).

When the plate body 221 is opened, the exhaust gas flows toward the exhaust pipe 100 without changing the cross-sectional area of the passage, and is mixed with the urea water injected from the urea water injection module 10.

Table 1 discloses the change in the flow rate of the exhaust gas according to the application of the present invention.

In the conventional exhaust structure for a diesel engine, even if there is a difference in the exhaust flow rate in a low load condition or a high load condition, there is no difference in the diameter and exhaust cross-sectional area of the exhaust pipe through which the exhaust gas passes, resulting in a large difference in the exhaust flow rate per unit area. The mixing efficiency of water was low.

In comparison, according to the present invention, since the valve plate 220 is closed in a low load state, the diameter of the exhaust pipe is reduced and the exhaust cross-sectional area is also reduced. As a result, the exhaust flow rate per unit area approximates the high load condition.

On the other hand, referring to Figure 5, it can be seen the effect of removing the uniformity of the spray and NOx of urea water according to the exhaust flow rate and the unit exhaust flow rate.

Fig. 5(a) is a spray uniformity (upper side) and a distribution table of NOx (lower side) in a low load state, where the number of urea is not uniformly mixed, and accordingly, a region with a small NOx (blue region on the upper distribution table) and many regions (red) Area).

In contrast, FIG. 5(b) shows the spray uniformity (upper side) and NOx distribution table (lower side) in a high load state, and the exhaust flow rate and the unit exhaust flow rate increase, whereby the urea water is sprayed relatively evenly, resulting in a high NOx concentration ( It can be seen that there are few regions).

At this time, according to the present invention, even in a low load state, since the exhaust flow rate per unit area is close to the high load state, the spray uniformity as shown in FIG. 5(b) and the distribution of NOx are realized.

Therefore, in the present invention, by increasing the flow rate of the exhaust gas in a low load state, there is an effect of effectively removing NOx by increasing the efficiency of mixing with urea water.

Although the present invention has been described in detail through specific embodiments, the present invention is for specifically describing the present invention, and the present invention is not limited thereto, and the present invention has ordinary knowledge in the field within the technical spirit of the present invention. It is clear that the modification and improvement are possible by the ruler.

All simple modifications or changes of the present invention belong to the scope of the present invention, and the specific protection scope of the present invention will be clarified by the appended claims.

10: urea water injection module
100: exhaust pipe
200: flow control unit
210: exhaust adapter
211: Pipe insert
212: plate opening and closing
220: valve plate
221: plate body
222: torsion spring
230: variable pipe
231: pipe body
232: stopper
233: pipe fixing

Claims (7)

An exhaust pipe formed to flow exhaust gas and installed with a urea water injection module; And
A flow rate control unit provided to control the flow rate of the exhaust gas flowing into the exhaust pipe;
Including,
The flow rate control unit,
An exhaust adapter provided to couple the exhaust pipe;
A variable pipe installed in the exhaust pipe, provided with an exhaust gas flowing therein, and formed to have an outer diameter smaller than the inner diameter of the exhaust pipe; And
A valve plate provided in the exhaust adapter and opened and closed to adjust a cross-sectional area of a flow path flowing into the exhaust pipe;
It includes,
The valve plate,
A plate body provided to be opened and closed by hydraulic pressure of exhaust gas;
Including,
The urea water injection module,
It is arranged corresponding to the position of the end portion in the direction in which the exhaust gas of the variable pipe is discharged,
The plate body,
Under the flow rate of the exhaust gas smaller than a predetermined flow rate, a space between the exhaust adapter and the outer circumferential surface of the variable pipe is blocked so that all the exhaust gas flows into the variable pipe, and exhaust gas having a flow rate higher than the predetermined flow rate is introduced. In the case, the exhaust structure for a diesel engine characterized in that it is open.
delete delete According to claim 1,
The valve plate,
A torsion spring fixed to one side of the exhaust adapter, the plate body and the other side being combined, and configured to apply a restoring force to the plate body;
Exhaust structure for a diesel engine further comprising a.
According to claim 1,
The variable pipe,
A pipe body provided with exhaust gas flowing therein; And
A stopper formed on an outer circumferential surface of the pipe body and protruding to support the valve plate when the valve plate is closed;
Exhaust structure for a diesel engine comprising a.
The method of claim 5,
The variable pipe,
A pipe fixing part extending from an outer circumferential surface of the pipe body and provided to be coupled to an inner circumferential surface of the exhaust pipe;
Exhaust structure for a diesel engine further comprising a.
delete

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