Exhaust gas heat exchanger capable of controlling cooling performance

Abstract

The present invention relates to an exhaust gas heat exchanger capable of controlling the cooling performance. The exhaust gas heat exchanger includes: a cooler through which cooling water flows and in which a plurality of gas tubes is provided to allow exhaust gas to flow; an intake and exhaust block including an intake part, a supply line, a discharge line, a bypass line, and a first flap; a U-turn block including an inflow part, a re-cooling line, a release line, and a second flap; and an air duct.

Claims

1. An exhaust gas heat exchanger comprising: a cooler through which cooling water flows and in which a plurality of gas tubes is provided to allow exhaust gas to flow; an intake and exhaust block including an intake part to which an exhaust gas pipe for supplying exhaust gas is connected, a supply line for communicating first ends of some of the plurality of gas tubes with the intake part, a discharge line for communicating first ends of the remaining tubes of the plurality of gas tubes with outside, a bypass line for bypassing exhaust gas entering from the intake part to the outside, and a first flap for blocking selectively any one line of the supply line and the bypass line; a U-turn block including an inflow part into which exhaust gas discharged through second ends of some of the plurality of gas tubes flows, a re-cooling line for communicating second ends of the remaining tubes of the plurality of gas tubes with the inflow part, a release line for discharging exhaust gas entering from the inflow part to the outside, and a second flap for blocking selectively any one line of the re-cooling line and the release line; and an air duct for guiding exhaust gas to the discharge line, the exhaust gas being discharged through the release line, wherein, a supply partition having a supply hole is provided in the supply line, a bypass partition having a bypass hole is provided in the bypass line, the first flap is rotatably mounted on the intake and exhaust block and is operated to cover the supply hole or the bypass hole depending on a rotational angle thereof, a re-cooling partition having a re-cooling hole is provided in the re-cooling line, a release partition having a release hole is provided in the release line, the second flap is rotatably mounted on the U-turn block and is operated to cover the re-cooling hole or the release hole depending on a rotational angle thereof, and outlets of the discharge line and the bypass line are integrally formed into a single pipe that is divided by a discharge partition.

2. The exhaust gas heat exchanger of claim 1, wherein number of the gas tubes connected to an outlet of the re-cooling line is larger than number of the gas tubes connected to an outlet of the supply line.

Description

DESCRIPTION OF DRAWINGS

(1) FIGS. 1 and 2 are sectional views showing a conventional exhaust gas heat exchanger.

(2) FIG. 3 is a sectional view showing an exhaust gas heat exchanger according to the present invention when the exhaust gas heat exchanger is in a cooling mode.

(3) FIG. 4 is a sectional view showing the exhaust gas heat exchanger according to the present invention when the exhaust gas heat exchanger is in a semi-cooling mode.

(4) FIG. 5 is a sectional view showing the exhaust gas heat exchanger according to the present invention when the exhaust gas heat exchanger is in a bypass mode.

MODE FOR INVENTION

(5) Hereinafter, an exhaust gas heat exchanger according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

(6) FIG. 3 is a sectional view showing the exhaust gas heat exchanger according to the present invention when the exhaust gas heat exchanger is in a cooling mode. FIG. 4 is a sectional view showing the exhaust gas heat exchanger according to the present invention when the exhaust gas heat exchanger is in a semi-cooling mode. FIG. 5 is a sectional view showing the exhaust gas heat exchanger according to the present invention when the exhaust gas heat exchanger is in a bypass mode.

(7) The exhaust gas heat exchanger according to the present invention is configured to be operated as follows. When exhaust gas is re-circulated to an engine in order to reduce NOx included in the exhaust gas, the exhaust gas heat exchanger selectively guides a flow direction of the exhaust gas. Thus, the exhaust gas is supplied to the engine after passing through a cooler 300, or the exhaust gas is directly supplied to the engine without passing through the cooler 300. The exhaust gas heat exchanger of the present invention has a feature to which a semi-cooling mode is added, so that the exhaust gas is cooled to a certain level and then supplied to the engine by passing through some of gas tubes 310 of the cooler 300 in the semi-cooling mode.

(8) That is, the exhaust gas heat exchanger of the present invention includes: the cooler 300 through which cooling water flows and in which a plurality of gas tubes 310 is provided to allow exhaust gas to flow; an intake and exhaust block 200 receiving exhaust gas through an exhaust gas pipe 100 and supplying the exhaust gas to the cooler 300; and a U-turn block 400 transferring exhaust gas that is cooled while passing through the cooler 300 to the intake and exhaust block 200. Exhaust gas supplied to the cooler 300 through the intake and exhaust block 200 is supplied to the U-turn block 400 through some of the gas tubes 310, without passing through all of the gas tubes 310 in the cooler 300. The exhaust gas supplied to the U-turn block 400 is transferred to the intake and exhaust block 200 passing through the remaining gas tubes 310, or not passing through the gas tubes 310, which characterizes the exhaust gas heat exchanger of the present invention.

(9) In order to enable the flow path described above, the intake and exhaust block 200 includes: an intake part 210 connected to the exhaust gas pipe 100; a supply line 220 for communicating each first end of some of the plurality of gas tubes 310 with the intake part 210; a discharge line 230 for communicating each first end of the remaining gas tubes of the plurality of gas tubes 310 with the outside; a bypass line 240 for bypassing exhaust gas flowing into the intake part 210 to the outside; and a first flap 250 for selectively closing any one of the supply line 220 and the bypass line 240.

(10) In addition, the U-turn block 400 includes: an inflow part 410 in which exhaust gas discharged through each second end of some of the plurality of gas tubes 310 flows; a re-cooling line 420 for communicating each second end of the remaining gas tubes of the plurality of gas tubes 310 with the inflow part 410; a release line 430 for discharging exhaust gas that flows through the inflow part 410 to the outside; and a second flap 440 for selectively closing any one of the re-cooling line 420 and the release line 430. In order to straightly transfer exhaust gas discharged through the release line 430 to the intake and exhaust block 200, a separate air duct 500 is provided in the exhaust gas heat exchanger of the present invention to communicate an outlet of the release line 430 with the discharge line 230.

(11) Meanwhile, in order to ensure firm closing of the first flap 250 regarding any one of the supply line 220 and the bypass line 240, a supply partition 222 having a supply hole 224 is provided in the supply line 220, and a bypass partition 212 having a bypass hole 244 is provided in the bypass line 240. In addition, the first flap 250 is rotatably provided in the intake and exhaust block 200, thereby covering the supply hole 224 or the bypass hole 244 depending on a rotational angle thereof. Therefore, when the first flap 250 is maximally rotated counterclockwise, the bypass hole 244 is covered by the first flap 250 so that the bypass line 240 is closed as shown in FIG. 3. In contrast, when the first flap 250 is maximally rotated clockwise, the supply hole 224 is covered by the first flap 250 so that the supply line 220 is closed as shown in FIG. 5.

(12) Likewise, in order to ensure effective closing of the second flap 440 regarding any one of the re-cooling line 420 and the release line 430, a re-cooling partition 422 having a re-cooling hole 424 is provided in the re-cooling line 420, and a release partition 432 having a release hole 434 is provided in the release line 430. In addition, the second flap 440 is rotatably provided in the U-turn block 400 to cover the re-cooling hole 424 or the release hole 434 depending on a rotational angle thereof. Therefore, when the second flap 440 is maximally rotated clockwise, the release hole 434 is covered by the second flap 440 so that the release line 430 is closed as shown in FIG. 3. In contrast, when the second flap 440 is maximally rotated counterclockwise, the re-cooling hole 424 is covered by the second flap 440 so that the re-cooling line 420 is closed as shown in FIG. 4.

(13) An exhaust gas cooling mode is determined by which lines are closed by the first flap 250 and the second flap. Hereinbelow, mode conversion due to operations of the first flap 250 and the second flap 440 will be described in detail.

(14) In a cooling mode as shown in FIG. 3, the first flap 250 is maximally rotated counterclockwise to cover the bypass hole 244 and the second flap 440 is maximally rotated clockwise to cover the release hole 434. In this mode, exhaust gas flowing through the exhaust gas pipe 100 is maximally cooled.

(15) That is, as shown in FIG. 3, when exhaust gas is supplied through the exhaust gas pipe 100 to the intake part 210 while the bypass line 240 and the release line 430 are closed, the exhaust gas flows along the supply line 220. Here, an outlet of the supply line 220 communicates only with some (in the embodiment, three upper gas tubes 310) of the plurality of gas tubes 310 provided in the cooler 300. Thus, the exhaust gas supplied to the cooler 300 through the supply line 220 is cooled while passing through the three upper gas tubes 310, and then enters the inflow part 410 of the U-turn block 400.

(16) As shown in FIG. 3, since the U-turn block 400 is composed of the closed release line 430 and the opened re-cooling line 420, the exhaust gas flowing through the inflow part 410 is returned to the cooler 300 through the re-cooling line 420 and is cooled again. Here, an outlet of the re-cooling line 420 communicates only with the remaining gas tubes 310 (in the embodiment, five lower gas tubes 310) of the plurality of gas tubes 310 provided in the cooler 300. Accordingly, the exhaust gas supplied to the cooler 300 through the re-cooling line 420 is not interfered with by exhaust gas entering the U-turn block 400.

(17) In addition, the exhaust gas that is cooled again while passing through the five lower gas tubes 310 is re-circulated to the engine through the discharge line 230. Here, a part of the exhaust gas flowing into the discharge line 230 may be returned to the U-turn block 400 through the air duct 500. However, since the release line 430 communicating with the air duct 500 is sealed by the second flap 440, backflow of exhaust gas does not occur.

(18) Meanwhile, exhaust gas returned to the cooler 300 from the re-cooling line 420 is further cooled to a certain level rather than exhaust gas supplied to the cooler 300 from the supply line 220. Accordingly, in order to more reliably cool exhaust gas returned to the cooler 300 from the re-cooling line 420, it is preferable that contact area between the exhaust gas and the gas tubes 310 is increased. That is, it is preferable that the number of gas tubes 310 connected to the outlet of the re-cooling line 420 is designed to be larger than the number of gas tubes 310 connected to the outlet of the supply line 220.

(19) In a semi-cooling mode as shown in FIG. 4, the first flap 250 is maximally rotated counterclockwise and covers the bypass hole 244, and the second flap 440 is also maximally rotated counterclockwise and covers the re-cooling hole 424. In this mode, exhaust gas supplied through the exhaust gas pipe 100 is cooled to a certain level.

(20) That is, as shown in FIG. 4, exhaust gas is supplied to the intake part 210 through the exhaust gas pipe 100 while the bypass line 240 and the re-cooling line 420 are closed. Here, the exhaust gas is cooled to the certain level by passing through some (in the embodiment, three upper gas tubes 310) of the plurality of gas tubes 310 provided in the cooler 300. Then, the exhaust gas flows directly to the discharge line 230 through the release line 430 and the air duct 500 without being returned to the cooler 300. Accordingly, the exhaust gas flowing into the discharge line 230 through the release line 430 and the air duct 500 is re-circulated to the engine while maintaining the temperature higher than the temperature in the cooling mode in FIG. 3.

(21) Therefore, when exhaust gas discharged from the engine needs to be slightly cooled and re-circulated to the engine, the exhaust gas heat exchanger of the present invention can be turned to the semi-cooling mode as shown in FIG. 4, and cool the exhaust gas to the certain level. Thus, situational NOx reduction effect can be maximized.

(22) In a bypass mode as shown in FIG. 5, the first flap 250 is maximally rotated clockwise and covers the supply hole 224. This bypass mode is a cooling mode in which exhaust gas supplied through the exhaust gas pipe 100 is maximally cooled so as to be circulated to the engine after being bypassed without being cooled.

(23) That is, exhaust gas is supplied to the intake part 210 through the exhaust gas pipe 100 while the supply line 220 is closed, as shown in FIG. 5. Thus, since the exhaust gas is bypassed to the outside of the intake and exhaust block 200 along the bypass line 240, the exhaust gas is re-circulated to the engine without any cooling process by the cooler 300. Here, the exhaust gas is not transferred toward the U-turn block 400 at all, and the exhaust gas can be bypassed regardless of which flow path is closed by the second flap 440.

(24) In the above-described case in which exhaust gas discharged from an exhaust manifold of the engine is again bypassed to an intake manifold of the engine, when the temperature of the exhaust gas is not very high such as when the engine is started, the problem that CO and HC are discharged without being converted into harmless gas can be solved. In addition, the effect on the problem may be obtained by the same way when the conventional exhaust gas heat exchanger is used, and a detailed description thereof will be omitted.

(25) Meanwhile, exhaust gas discharged to the outside of the intake and exhaust block 200 through an outlet of the discharge line 230 or an outlet of the bypass line 240 is supplied to the intake manifold of the engine through a separate transfer pipe (not shown). In order to supply both exhaust gases discharged from outlets of the discharge line 230 and the bypass line 240 to the intake manifold of the engine using one transfer pipe, it is preferable that the outlets of the discharge line 230 and the bypass line 240 are each formed as a semicircular-shaped cross-section of flow path so as to be coupled in a single pipe. Of course, the outlets of the discharge line 230 and the bypass line 240 should be separated by a discharge partition 232 so as not to directly communicate with each other.

(26) Although a preferred embodiment of the present invention has been described for illustrative purposes, the scope of the present invention is not limited to the specific embodiment, but should be interpreted according to the accompanying claims. Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.