JP2019027403A - Two-stage supercharging system - Google Patents

Abstract

To provide a two-stage supercharging system capable of protecting a high-pressure stage compressor from the phenomenon that oil content or condensate water accumulated in a low-pressure stage intercooler are collectively suctioned to collide with each other.SOLUTION: A two-stage supercharging system comprises a high-pressure stage turbocharger 6 and a low-pressure stage turbocharger 10, wherein a low-pressure stage intercooler 12 is arranged relatively higher than a high-pressure stage intercooler 13; and the low-pressure stage intercooler 12 and the high-pressure stage intercooler 13 are connected through a communication pipe 17 so as to extract oil content or condensate water accumulated in the low-pressure stage intercooler 12 with gravity in a period where an engine 1 stops.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a two-stage supercharging system.

  In recent years, a two-stage supercharging system has been proposed from the viewpoint of realizing downsizing and torque increase of the supercharging system. In this type of two-stage supercharging system, as shown in FIG. The high-pressure stage turbocharger 6 that operates the high-pressure stage turbine 3 by the exhaust G sent from the engine and supplies the intake air A compressed by the high-pressure stage compressor 4 to the intake manifold 5 of the engine 1, and the high pressure of the high-pressure stage turbocharger 6 A low-pressure stage turbocharger 10 that operates the low-pressure stage turbine 8 by the exhaust G sent from the stage turbine 3 and supplies the intake air A compressed by the low-pressure stage compressor 9 to the high-pressure stage compressor 4 is provided.

  Further, a low pressure stage intercooler 12 is interposed between the discharge side of the low pressure stage compressor 9 of the low pressure stage turbocharger 10 and the suction side of the high pressure stage compressor 4 of the high pressure stage turbocharger 6. A high-pressure stage intercooler 13 is interposed between the discharge side of the high-pressure stage compressor 4 and the intake manifold 5 of the engine 1.

  Also, an EGR pipe 14 is provided from the upstream side of the high-pressure stage turbine 3 (specifically, the exhaust manifold 2) to the downstream side (specifically, the intake manifold 5) of the high-pressure stage intercooler 13, The EGR pipe 14 is provided with an EGR cooler 15 that cools the exhaust gas G diverted from the exhaust system, and an EGR valve 16 that adjusts the flow rate of the exhaust G to be returned to the intake system.

  Thus, in such a two-stage supercharging system, during operation of the engine 1, the exhaust G sent from the exhaust manifold 2 flows into the high-pressure turbine 3 and drives the high-pressure compressor 4, and then the low-pressure stage. The intake air A that flows into the turbine 8 and drives the low-pressure compressor 9 and is compressed by flowing into the low-pressure compressor 9 is supplied to the high-pressure compressor 4 through the low-pressure intercooler 12, and the high-pressure compressor 4 is compressed again and fed to the intake manifold 5 via the high-pressure intercooler 13, so that the amount of intake A delivered to the cylinder increases, and if the fuel injection amount per cycle is increased, the engine 1 Can increase the output.

  Further, a part of the exhaust G flows from the exhaust manifold 2 into the EGR pipe 14, and the exhaust G cooled by the EGR cooler 15 and adjusted in flow rate by the EGR valve 16 is combined with the intake air A with the intake manifold 5. This reduces the combustion temperature in the cylinder and reduces the generation of NOx.

  However, in the high speed and high load range where the flow rate of the exhaust G is large, the high pressure turbocharger 6 rotates excessively and the boost pressure increases more than necessary, and the maximum in-cylinder pressure of each cylinder of the engine 1 exceeds the limit value. There is a possibility that the exhaust pressure becomes higher than the pressure of the exhaust manifold 2 and the exhaust G cannot be recirculated.

  Therefore, a bypass pipe 7 that bypasses the high-pressure turbine 3 is provided, and a bypass valve 11 is provided in the middle of the bypass pipe 7, and the bypass valve 11 is opened in a high-speed and high-load region so that only the exhaust gas G having an appropriate flow rate is high pressure. It flows through the stage turbine 3, and the remainder is bypassed to the high pressure stage turbine 3 and led to the low pressure stage turbine 8.

  The prior art document information related to this type of two-stage supercharging system includes the following Patent Document 1.

Japanese Utility Model Publication No.59-2926

  However, in the engine 1 in recent years, the blow-by gas leaking from the combustion chamber into the crankcase is returned to the intake system without being released to the atmosphere, and is incinerated by the engine 1, so that the mist contained in the blow-by gas is contained. Oil and condensed water are stored in droplets in the low-pressure stage intercooler 12, the accumulated oil and condensed water are sucked into the high-pressure stage compressor 4 of the high-pressure stage turbocharger 6 at a stroke. There is concern that it will adversely affect the health of the company.

  That is, in the case of the one-stage supercharging so far, since the engine 1 is the destination of the oil and condensed water accumulated in the intercooler, the oil and condensed water sucked into the engine 1 is merely incinerated. Although there was no problem in particular, in the case of two-stage supercharging, the high-pressure stage compressor 4 is the destination of the oil and condensed water collected in the preceding low-pressure stage intercooler 12, so that the high-pressure stage compressor 4 will collide with the blades of the high-pressure compressor 4 with a much larger amount of oil or condensed water than the air normally handled in 4 and the blades will be greatly damaged by this collision. There was a possibility.

  The present invention has been made in view of the above circumstances, and provides a two-stage turbocharging system capable of protecting a high-pressure compressor from an event in which oil or condensed water accumulated in the low-pressure intercooler is sucked at once and collides. With the goal.

  The present invention includes a high-pressure stage turbocharger that operates a high-pressure stage turbine by exhaust gas sent from an engine and that compresses the intake air compressed by a high-pressure stage compressor to the engine via a high-pressure stage intercooler, and is sent from the high-pressure stage turbine. A two-stage supercharging system comprising: a low-pressure stage turbocharger that operates a low-pressure stage turbine by exhaust gas and supplies the compressed air compressed by the low-pressure stage compressor to the high-pressure stage compressor via a low-pressure intercooler, The low-pressure stage intercooler is arranged so as to be relatively higher than the high-pressure stage intercooler, and the oil and condensed water accumulated in the low-pressure stage intercooler can be extracted using gravity when the engine is stopped. A cooler and the high-pressure stage intercooler are connected by a connecting pipe. Is shall.

  In this way, when the engine is stopped, the oil or condensed water accumulated in the low pressure intercooler flows down through the connecting pipe due to gravity and is extracted to the high pressure intercooler. This prevents an amount of oil and condensed water from accumulating, and prevents the oil and condensed water from being sucked into the high-pressure stage compressor from the low-pressure intercooler and colliding with each other.

  On the other hand, when the engine is in operation, intake air escapes from the high pressure stage intercooler side through the connecting pipe to the low pressure stage intercooler side. However, oil and condensed water collected in the low pressure stage intercooler is removed when the engine is stopped. The diameter of the connecting pipe should be narrowed to the minimum necessary within the range where it can flow down under its own weight, and if such a minimum required diameter is set, the low pressure stage intercooler from the high pressure stage intercooler side during engine operation. The amount of intake air bypassing to the cooler side is extremely small.

  The oil and condensed water extracted to the high-pressure stage intercooler will be sucked into the engine and incinerated depending on the operating conditions, but will be damaged to the extent that the oil and condensed water collide with the engine. Since there is no such weak point, it is not necessary to take measures against collision of oil and condensed water after the high-pressure intercooler as before.

  In the present invention, it is preferable to provide an orifice in the middle of the connecting pipe that suppresses the amount of intake air that escapes from the high-pressure stage intercooler to the low-pressure stage intercooler during engine operation. It is not necessary to use the minimum necessary diameter as described above, and the intake air bypass amount can be suppressed by selecting an orifice having an appropriate diameter and providing it in the middle of the connecting pipe.

  According to the above-described two-stage supercharging system of the present invention, various excellent effects as described below can be obtained.

  (I) According to the invention described in claim 1 of the present invention, the oil component and the condensed water are not collected in the low pressure stage intercooler, and the oil component and the condensed water are collected from the low pressure stage intercooler. Since it is possible to avoid an event where the compressor is sucked into the compressor at a stroke, it is possible to reliably protect the high-pressure compressor from such an event, and to ensure the soundness of the high-pressure compressor for a long period of time. it can.

  (II) According to the invention described in claim 2 of the present invention, the orifice of the connecting pipe is not particularly restricted, and an orifice having an appropriate diameter is selected and provided in the middle of the connecting pipe. It is possible to suppress the amount of intake air bypassing from the high pressure stage intercooler side to the low pressure stage intercooler side during engine operation.

It is the schematic which shows an example of the form which implements this invention. It is an enlarged view which shows the detail of the principal part of FIG. It is the schematic which shows a prior art example.

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

  1 and FIG. 2 show an example of an embodiment for carrying out the present invention, and the parts denoted by the same reference numerals as those in FIG. 3 represent the same items, and in the same manner as the conventional example described in FIG. A high-pressure stage turbocharger 6 for operating the high-pressure stage turbine 3 by exhaust G delivered from the engine 1 and supplying the intake air A compressed by the high-pressure stage compressor 4 to the engine 1 via the high-pressure stage intercooler 13; A low-pressure stage turbocharger 10 that operates the low-pressure stage turbine 8 by the exhaust G delivered from the turbine 3 and supplies the intake air A compressed by the low-pressure stage compressor 9 to the high-pressure stage compressor 4 via the low-pressure intercooler 12. The low-pressure stage intercooler 12 is arranged so as to be relatively higher than the high-pressure stage intercooler 13. A characteristic is that the low pressure stage intercooler 12 and the high pressure stage intercooler 13 are connected by a connecting pipe 17 so that oil and condensed water accumulated in the low pressure stage intercooler 12 can be extracted by using gravity. Yes.

  That is, in FIG. 1, the high-pressure stage intercooler 13 and the low-pressure stage intercooler 12 are schematically shown in parallel. However, as shown in FIG. 2, the low-pressure stage intercooler 12 is arranged in the upper stage. The upper low-pressure stage intercooler 12 and the lower high-pressure stage intercooler 13 are arranged so that the intake air A flows in the same direction in the horizontal direction. The intake inlets 12a, 13a and the intake outlets 12b, 13b are close to each other on the same side, so that the intake outlets 12b, 13b that are likely to collect oil and condensed water are made compact by a relatively short communication pipe 17. It can be connected.

  Further, in the present embodiment, the orifice 18 for narrowing the flow path to the minimum necessary within a range in which the oil or condensed water accumulated in the low pressure intercooler 12 can flow down by its own weight when the engine 1 is stopped is provided in the connecting pipe. 17, the orifice 18 suppresses the bypass amount of the intake air A from the high pressure stage intercooler 13 side to the low pressure stage intercooler 12 side when the engine 1 is operated.

  Here, it is preferable to employ a resin tube or the like having poor wettability (wetability: mainly affinity of the liquid with respect to the solid surface), for example, as the communication tube 17. Oil and condensed water droplets easily flow down in the tube 17.

  In FIG. 2, the low-pressure stage intercooler 12 and the high-pressure stage intercooler 13 are illustrated as an image in which the intake air A is cooled by air cooling with traveling wind or the like from a direction perpendicular to the drawing. Of course, either one or both may be configured to be water-cooled by heat exchange with cooling water.

  Thus, if the two-stage supercharging system is configured in this way, the oil or condensed water accumulated in the low-pressure intercooler 12 when the engine 1 is stopped flows down through the connecting pipe 17 due to gravity to the high-pressure intercooler 13. As a result, the amount of oil and condensed water collected in the low-pressure intercooler 12 does not accumulate, and the oil and condensed water are sucked into the high-pressure compressor 4 from the low-pressure intercooler 12 and collide with each other. To be avoided.

  On the other hand, when the engine 1 is in operation, the intake air A flows out from the high pressure stage intercooler 13 side to the low pressure stage intercooler 12 side through the connecting pipe 17, but in this embodiment, the low pressure stage intercooler is discharged. Since the flow path is narrowed to the minimum necessary by the orifice 18 within a range in which the oil or condensed water accumulated in 12 can flow under its own weight when the engine 1 is stopped, the high-pressure stage intercooler 13 is operated when the engine 1 is operated. The bypass amount of the intake air A that escapes from the side to the low-pressure stage intercooler 12 side is extremely small.

  Here, in order to suppress the bypass amount of the intake air A that escapes from the high-pressure stage intercooler 13 side to the low-pressure stage intercooler 12 side during the operation of the engine 1, the connecting pipe 17 itself has the minimum necessary diameter as described above. However, if the orifice 18 is used as in the present embodiment, the connecting pipe 17 itself does not need to have the required minimum diameter as described above, and the bypass amount of the intake air A can be easily suppressed. Is possible.

  The oil and condensed water extracted to the high-pressure stage intercooler 13 are sucked into the engine 1 and incinerated depending on the operating conditions. However, the oil and condensed water collide with the engine 1 side. Since there is no fragile part that is damaged, it is not necessary to take measures against collision of oil and condensed water after the high-pressure intercooler 13 as before.

  Therefore, according to the above-described embodiment, the oil component and the condensed water are not sucked into the low pressure stage intercooler 12 and the oil component and the condensed water are sucked into the high pressure stage compressor 4 from the low pressure stage intercooler 12 at once. Therefore, the high-pressure stage compressor 4 can be reliably protected from such an event, and the soundness of the high-pressure stage compressor 4 can be ensured over a long period of time.

  In particular, in the present embodiment, the diameter of the connecting pipe 17 is not particularly restricted, and an orifice 18 having an appropriate diameter is selected and provided in the middle of the connecting pipe 17. The bypass amount of the intake air A that flows out from the high-pressure stage intercooler 13 side to the low-pressure stage intercooler 12 side can be suppressed.

  The two-stage supercharging system of the present invention is not limited to the above-described embodiment. If the connecting pipe can have an appropriate diameter, it is not always necessary to provide an orifice in the middle of the connecting pipe. Of course, various modifications can be made without departing from the scope of the present invention.

1 Engine 3 High-pressure stage turbine 4 High-pressure stage compressor 6 High-pressure stage turbocharger 8 Low-pressure stage turbine 9 Low-pressure stage compressor 10 Low-pressure stage turbocharger 12 Low-pressure stage intercooler 13 High-pressure stage intercooler 17 Connecting pipe 18 Orifice A Intake G Exhaust gas

Claims (2)

  A high-pressure stage turbocharger that operates the high-pressure stage turbine by exhaust gas sent from the engine and supplies the intake air compressed by the high-pressure stage compressor to the engine via the high-pressure stage intercooler, and low pressure by the exhaust gas sent from the high-pressure stage turbine A two-stage supercharging system comprising: a low-pressure stage turbocharger that operates a stage turbine and feeds the intake air compressed by the low-pressure stage compressor to the high-pressure stage compressor via a low-pressure stage intercooler. Is arranged so as to be relatively higher than the high-pressure stage intercooler, and the low-pressure stage intercooler and the high-pressure stage can be extracted using gravity when the engine is stopped. Two-stage excess characterized by connecting to the stage intercooler with a connecting pipe System.   2. The two-stage turbocharging system according to claim 1, wherein an orifice that suppresses a bypass amount of intake air that escapes from the high-pressure stage intercooler side to the low-pressure stage intercooler side during engine operation is provided in the middle of the connecting pipe.

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