JP2017141673A - Cooling efficiency recovery method and device for egr cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover during operation cooling efficiency of an EGR cooler, which deteriorated due to continuous running under a severe condition at high-speed and heavy load.SOLUTION: An EGR cooler 16 includes a tube 3 and a shell 1 enclosing the tube 3, and is configured to supply/discharge cooling water 10 to/from the inside of the shell 1 and pass exhaust gas 13 through the tube 3 to perform heat exchange between the cooling water 10 and the exhaust gas 13. A cooling efficiency recovery method of the EGR cooler comprises stopping circulation of the exhaust gas 13 to the EGR cooler 16, and temporarily switching and introducing the cooling water 10 stored at a room temperature or less to the EGR cooler 16.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cooling efficiency recovery method and apparatus for an EGR cooler.

  Conventionally, an EGR device that reduces the generation of nitrogen oxides by recirculating a part of exhaust gas of an engine such as an automobile to the engine is known. In such an EGR device, the exhaust gas recirculated to the engine is known. When the engine is cooled, the temperature of the exhaust gas is reduced and the volume of the exhaust gas is reduced, so that the combustion temperature can be lowered and the generation of nitrogen oxides can be effectively reduced without significantly reducing the output of the engine. Some engines are equipped with an EGR cooler for cooling the exhaust gas in the middle of the line for recirculating the exhaust gas to the engine.

  FIG. 4 is a cross-sectional view showing an example of the EGR cooler, in which 1 denotes a shell formed in a cylindrical shape, and a plate is attached to both ends of the shell 1 in the axial direction so as to close the end face of the shell 1. 2 and 2 are fixed, and both ends of a large number of tubes 3 are fixed to the respective plates 2 and 2 in a penetrating state. The large numbers of tubes 3 extend in the axial direction inside the shell 1. Yes.

  A cooling water inlet pipe 4 is attached from the outside near one end of the shell 1, and a cooling water outlet pipe 5 is attached from the outside near the other end of the shell 1. The cooling water 10 led through 9 is supplied from the cooling water inlet pipe 4 to the inside of the shell 1, flows outside the tube 3, and is discharged from the cooling water outlet pipe 5 to the outside of the shell 1 through the drain pipe 11. It has become.

  Further, bonnets 6, 6 formed in a bowl shape are fixed to the opposite shell 1 side of each plate 2, 2 so as to enclose the end faces of the respective plates 2, 2, and in the center of one bonnet 6. The exhaust gas inlet 7 is provided in the center of the other bonnet 6 and the exhaust gas outlet 8 is provided in the center of the other bonnet 6. The exhaust gas 13 led from the exhaust manifold (not shown) through the EGR pipe 12 on the inlet side is provided from the exhaust gas inlet 7. After being cooled by heat exchange with the cooling water 10 flowing outside the tubes 3 while passing through a large number of tubes 3, they are discharged into the other bonnet 6 and exhaust gas outlet 8. Is recirculated to the intake manifold (not shown) through the EGR pipe 14 on the outlet side. Reference numeral 15 denotes an EGR valve provided in the outlet EGR pipe 14.

  In the figure, reference numeral 5a denotes a bypass outlet pipe provided at a position facing the cooling water inlet pipe 4 in the diameter direction of the shell 1, and a part of the cooling water 10 passes through the drain pipe 11a from the bypass outlet pipe 5a. By extracting, the stagnation of the cooling water 10 is prevented from occurring at a location facing the cooling water inlet pipe 4.

  As prior art document information related to this type of EGR cooler, there is Patent Document 1 below.

JP 2002-39019 A

  However, in such an EGR cooler, when the continuous operation is performed under severe conditions of high speed and high load, the exhaust gas 13 containing a large amount of water passes through the tube 3. As a result, the exhaust gas 13 is gradually accumulated and the cooling efficiency of the exhaust gas 13 is lowered. As a result, the exhaust gas 13 recirculated to the intake manifold is increased in volume and the substantial EGR rate is lowered. There was a fear of being invited.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to recover the cooling efficiency of the EGR cooler, which has been lowered by continuous operation under severe conditions of high speed and high load, during operation.

  The present invention includes a tube and a shell that surrounds the tube, supplies and discharges cooling water into the shell, and exchanges heat between the exhaust gas and the cooling water through the exhaust gas in the tube. A method for recovering the cooling efficiency of the EGR cooler, wherein the flow of exhaust gas to the EGR cooler is stopped and the cooling water stored at room temperature or lower is temporarily switched to the EGR cooler and introduced. It is characterized by.

  Thus, when cooling water at a room temperature or lower is forcibly introduced into the EGR cooler in which the flow of exhaust gas is stopped in this way, the temperature in the tube temporarily decreases to a cold state and condensation occurs. The soot that has been deposited and deposited over the entire circumference of the inner peripheral surface of the tube flows down including condensed water, and most of the inner peripheral surface of each tube is returned from the covering state by the soot to the exposed state, and the EGR cooler The cooling efficiency is restored.

  Further, the present invention includes a tube and a shell surrounding the tube, supplies and discharges cooling water into the shell, and exchanges heat between the exhaust gas and the cooling water through the exhaust gas in the tube. A cooling efficiency recovery device for an EGR cooler, comprising: an EGR valve capable of stopping the flow of exhaust gas to the EGR cooler; and a water tank capable of storing cooling water at a room temperature or lower, and the water tank The cooling water stored at room temperature or lower can be temporarily switched to the EGR cooler and introduced.

  Thus, in this way, the flow of exhaust gas to the EGR cooler is stopped by the EGR valve, and the cooling water stored in the water tank at room temperature or lower is temporarily switched to the EGR cooler. This allows the inside of the tube to temporarily cool to a cold state to cause condensation, and the condensed water that adheres and accumulates on the entire circumference of the inner periphery of the tube is contained in condensed water. It is possible to recover the cooling efficiency of the EGR cooler by flowing down and returning the most part of the inner peripheral surface of each tube from the coated state to the exposed state.

  According to the above-described method and apparatus for recovering the cooling efficiency of the EGR cooler of the present invention, even if the cooling efficiency of the EGR cooler decreases due to continuous operation under high-speed and high-load severe conditions, the EGR cooler in which the circulation of the exhaust gas is stopped By forcibly introducing cooling water at room temperature or lower, the temperature inside the tube is temporarily lowered to a cold state to cause condensation, and the applicator was deposited and deposited over the entire circumference of the inner peripheral surface of the tube. As a result, the cooling efficiency of the EGR cooler can be recovered during operation.

It is the schematic which shows an example of the form which implements this invention. It is the schematic which shows the state which switched the three-way valve of FIG. It is a graph which shows the test result regarding this form example. It is sectional drawing which shows an example of a common EGR cooler.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIGS. 1 and 2 show an example of an embodiment of the present invention. The parts denoted by the same reference numerals as those in FIG. 4 represent the same parts, and 16 in the figure is configured in substantially the same manner as FIG. The EGR cooler 17 is an engine on which the EGR cooler 16 is mounted. A part of the cooling water 10 used for cooling the engine 17 is extracted and the shell 1 of the EGR cooler 16 is passed through the water supply pipe 9. A bypass passage 18 is provided in parallel with the water supply pipe 9, and a water tank that can store the cooling water 10 at room temperature or lower is provided in the middle of the bypass passage 18. 19 is equipped.

  That is, the bypass channel 18 is configured such that the flow of the cooling water 10 is blocked by the three-way valve 20 provided at the junction with the water supply pipe 9, and as shown in FIG. Is selected so that the cooling water 10 from the engine 17 is guided into the shell 1 of the EGR cooler 16, but the bypass flow path 18 is selected by switching the three-way valve 20 as shown in FIG. Thus, the cooling water 10 is guided into the shell 1 of the EGR cooler 16 via the water tank 19.

  Here, the cooling water 10 flowing through the bypass channel 18 is introduced into the bottom of the water tank 19 and extracted from the top of the water tank 19, and the bypass channel 18 is connected to the three-way valve. At the initial stage of opening by 20, the cooling water 10 having a normal temperature or less stored in the water tank 19 is sent out in advance.

  In addition, a large number of air-cooling fins 21 are formed on the side surface of the water tank 19 so that the internal cooling water 10 is air-cooled by traveling wind or the like, and the bypass flow path 18 is provided with the three-way valve. While being blocked by 20, the cooling water 10 stored in the water tank 19 is cooled to a room temperature or lower.

  In the figure, reference numeral 15 denotes an EGR valve provided in the EGR pipe 14 that guides the exhaust gas 13 that has passed through the EGR cooler 16 to the intake system, and the exhaust gas 13 flows to the EGR cooler 16 by closing the EGR valve 15. Is to be stopped.

  Thus, when the applicability gradually accumulates in the tube 3 due to continuous operation under severe conditions of high speed and high load, and the cooling efficiency of the exhaust gas 13 is lowered, the EGR valve 15 is closed to the EGR cooler 16. When the flow of the exhaust gas 13 is stopped and the bypass flow path 18 is selected by switching the three-way valve 20 and the cooling water 10 is caused to flow through the water tank 19, the water tank 19 is stored at room temperature or lower. The cooling water 10 that has been prepared is introduced into the shell 1 of the EGR cooler 16. As a result, the temperature in the tube 3 is temporarily reduced to a cold state to cause condensation, and the entire circumference of the inner peripheral surface of the tube 3 is condensed. The soot that has been deposited and deposited over the entire surface flows down including the condensed water, and most of the inner peripheral surface of each tube 3 is returned from the covering state by the soaking to the exposed state, and the EGR cooler 16 is cooled. So that the rate is restored.

  Here, when the particulate filter is mounted in the middle of the exhaust pipe not shown in FIGS. 1 and 2, the fuel is added to the oxidation catalyst provided in the preceding stage of the particulate filter, and It is necessary to perform forced regeneration of the particulate filter. Generally, when forced regeneration of the particulate filter is performed, the EGR valve 15 is closed and the exhaust gas recirculation is stopped. It is efficient if recovery of the EGR cooler 16 is attempted.

FIG. 3 shows the test results actually performed by the present inventor. The cooling efficiency of the EGR cooler 16 is measured at the time t ₀ when the engine load is increased and a stable state is reached after several seconds from the start of the test. When measured as an initial value, the cooling efficiency of the EGR cooler 16 gradually decreases from the initial value over time, but the cooling water 10 stored at room temperature or lower is temporarily stored in the EGR cooler 16. If the water temperature forced cooling operation in which the water temperature is forcibly lowered by sandwiching between the two is introduced, the cooling efficiency of the EGR cooler 16 is restored to the initial value at a time t _{1 that} can be regarded as the same measurement conditions as t _0. Excellent results were obtained.

  Here, when the cooling water 10 stored at room temperature or lower is temporarily switched to the EGR cooler 16 and introduced, the engine load is almost removed from the test safety. It is added that there is no control for removing the engine load when applied to an actual machine.

However, in this test, the engine load is almost removed in accordance with the water temperature forced cooling operation, so the engine load is increased to the level at the start of the test again after the water temperature forced cooling operation is sandwiched, and then stable for several seconds. The time t ₁ when the state is reached is regarded as the same measurement condition as the time t ₀ .

  The phenomenon that the cooling efficiency of the EGR cooler 16 recovers when the water temperature of the cooling water 10 is lowered to a cold state after the engine 17 is stopped has been already found by the inventors' earnest research and keen insight. However, this test result verified that the cooling efficiency of the EGR cooler 16 was recovered even if this was forcibly reproduced during operation.

  Therefore, according to the above embodiment, even if the cooling efficiency of the EGR cooler 16 is reduced due to continuous operation under severe conditions of high speed and high load, the cooling of the EGR cooler 16 in which the circulation of the exhaust gas 13 is stopped is below normal temperature. By forcibly introducing the water 10, the temperature in the tube 3 is temporarily lowered to a cold state to cause condensation, and the water deposited and deposited over the entire circumference of the inner peripheral surface of the tube 3 is condensed water. Therefore, the cooling efficiency of the EGR cooler 16 can be recovered during operation.

  The cooling efficiency recovery method and apparatus for the EGR cooler according to the present invention are not limited to the above-described embodiments, and various changes can be made without departing from the scope of the present invention.

1 Shell 3 Tube 10 Cooling Water 13 Exhaust Gas 15 EGR Valve 16 EGR Cooler 17 Engine 18 Bypass Channel 19 Water Tank

Claims (2)

  An EGR cooler comprising a tube and a shell surrounding the tube, wherein cooling water is supplied to and discharged from the inside of the shell, and heat is exchanged between the exhaust gas and the cooling water through the exhaust gas in the tube. A cooling efficiency recovery method, characterized in that the flow of exhaust gas to the EGR cooler is stopped and the cooling water stored at room temperature or lower is temporarily switched and introduced to the EGR cooler. Cooling efficiency recovery method for EGR cooler.   An EGR cooler comprising a tube and a shell surrounding the tube, wherein cooling water is supplied to and discharged from the inside of the shell, and heat is exchanged between the exhaust gas and the cooling water through the exhaust gas in the tube. A cooling efficiency recovery device, comprising: an EGR valve capable of stopping the flow of exhaust gas to the EGR cooler; and a water tank capable of storing cooling water at room temperature or lower, and storing the water tank at room temperature or lower. An apparatus for recovering cooling efficiency of an EGR cooler, characterized in that the cooled cooling water can be temporarily switched and introduced into the EGR cooler.

Images