JP2012197716A - Exhaust loss recovery device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve exhaust gas recirculation at a high EGR rate while performing supercharging by a supercharging system, and to ensure intake air volume required for combustion without extremely increasing exhaust pressure.SOLUTION: An exhaust loss recovery device is applied to an engine 1 including the supercharging system and an EGR line 11. The supercharging system is constituted of a low-pressure stage turbocharger 15 and a high-pressure stage turbocharger 14 which functions as a variable nozzle turbocharger, and the EGR line 11 connects between an exhaust manifold 9 and an intake manifold 7 to recirculate a part of exhaust gas 8 as EGR gas 8'. The exhaust loss recovery device includes: an EGR turbocharger 16 driving a turbine 16b by the EGR gas 8', compressing intake air 4 by a compressor 16a, and introducing the compressed intake air to the upstream side of the supercharging system of an intake system; a bypass line 19 bypassing the turbine 16b of the EGR turbocharger and allowing the EGR gas 8' to flow; and a bypass valve 20 opening/closing the bypass line.

Description

  The present invention relates to an exhaust loss recovery device.

  2. Description of the Related Art Conventionally, in an automobile engine or the like, a part of exhaust gas is extracted from the exhaust side and returned to the intake side, and combustion of fuel in the engine is suppressed by the exhaust gas returned to the intake side so that the combustion temperature is increased. So-called exhaust gas recirculation (EGR) is performed in which the generation of NOx is reduced by lowering.

  FIG. 2 shows an example of the EGR device for performing the above-described exhaust gas recirculation. In FIG. 2, reference numeral 1 denotes an engine that is a diesel engine equipped with a turbocharger 2 as a supercharging system, and intake air introduced from an air cleaner 3. 4 is sent to the compressor 2a of the turbocharger 2 through the intake pipe 5, the intake air 4 pressurized by the compressor 2a is sent to the intercooler 6 to be cooled, and the intake air from the intercooler 6 to the intake manifold 7 is further taken in. 4 is distributed to each cylinder of the engine 1.

  Further, the exhaust gas 8 discharged from each cylinder of the engine 1 is sent to the turbine 2b of the turbocharger 2 through the exhaust manifold 9, and the exhaust gas 8 driving the turbine 2b is sent to the outside of the vehicle through the exhaust pipe 10. To be discharged.

  The exhaust manifold 9 and the intake manifold 7 are connected by an EGR line 11 so that a part of the exhaust gas 8 can be extracted from the exhaust manifold 9 as the EGR gas 8 ′ and guided to the intake pipe 5. .

  Here, the EGR line 11 is equipped with an EGR valve 12 that appropriately opens and closes the EGR line 11 and an EGR cooler 13 for cooling the recirculated EGR gas 8 ′. The temperature of the EGR gas 8 ′ can be lowered by heat exchange between the cooling water and the EGR gas 8 ′, and the combustion temperature is lowered by recirculation of the water-cooled EGR gas 8 ′ to the engine 1. Can be planned.

  However, in the engine 1 with the turbocharger 2 as described above, since the intake side is supercharged, the pressure difference from the exhaust side is reduced in the high speed rotation region or the like, and it is difficult to realize a high EGR rate. However, as the turbocharger 2, a multi-vane type variable nozzle turbo (which has an annular nozzle nozzle on the turbine 2b side that can be adjusted in angle so that the nozzle opening can be arbitrarily changed) A variable geometry turbocharger), and if necessary, the nozzle opening on the turbine 2b side is narrowed down to increase the passage resistance of the exhaust gas 8 at the nozzle, thereby increasing the pressure of the exhaust manifold 9 to increase the pressure on the intake side and the exhaust side. The pressure difference is secured.

  However, the operation of increasing the pressure of the exhaust manifold 9 by narrowing the nozzle opening on the turbine 2b side is also an operation of increasing the rotational speed of the turbine 2b by increasing the rotational speed of the exhaust gas 8 in the turbine 2b. Although the outlet pressure (supercharging pressure) also increases, the efficiency of the turbine 2b deteriorates, so that the exhaust manifold 9 has a higher pressure rise than the outlet of the compressor 2a. A pressure difference between the intake side and the exhaust side is ensured in a high pressure region, and a high EGR rate is realized.

  Prior art document information disclosing an example in which a part of the exhaust gas 8 extracted from the exhaust manifold 9 is recirculated to the intake pipe 5 includes the following Patent Document 1.

JP 2001-123889 A

  However, if the exhaust gas recirculation is performed while ensuring the pressure difference between the exhaust side and the intake side in such a relatively high pressure region, a large amount of EGR gas 8 'can be recirculated, and a high EGR rate can be obtained. On the other hand, the intake 4 (fresh air) becomes difficult to enter, and there is a risk that the intake 4 required for combustion may be insufficient in quantity. Therefore, the opening of the EGR valve 12 can be secured to ensure the necessary amount of intake 4. Measures are taken to reduce the recirculation amount of the EGR gas 8 ′, but the relationship between the exhaust side and the intake side balanced by recirculation of a large amount of EGR gas 8 ′ is the above-mentioned EGR. By narrowing down the opening of the valve 12, the exhaust pressure of the engine 1 becomes an extreme state that is significantly higher than the supercharging pressure. This increases the exhaust resistance of the engine 1 and causes an excessive pumping loss, resulting in an increase in fuel consumption. Cause a significant deterioration There is a problem that put away is.

  In recent years, in order to realize downsizing and torque increase of the supercharging system, there is a type in which the supercharging system is a two-stage supercharging system composed of a high-pressure stage turbocharger and a low-pressure stage turbocharger. In such a two-stage supercharging system, the pressure ratio is higher than that of the single-stage type shown in the figure, so that the necessary amount of intake air 4 can be secured in the operating state as described above. If the opening degree of the EGR valve 12 is narrowed down, there is a possibility that the pumping loss is further excessive and the fuel consumption is further deteriorated.

  The present invention has been made in view of the above circumstances, and realizes exhaust gas recirculation at a high EGR rate while performing supercharging by a supercharging system, and extremely increases the amount of intake air necessary for combustion. It aims to secure without incurring.

  The present invention relates to a supercharging system comprising a turbocharger having an appropriate number of stages and at least the most upstream turbocharger of the exhaust system being a variable nozzle turbo capable of adjusting the nozzle opening of a turbine, and an exhaust manifold and an intake manifold. An exhaust loss recovery device for application to an engine having an EGR line that recirculates part of the exhaust gas as EGR gas from the exhaust side to the intake side by connecting the two, and the EGR gas flowing through the EGR line The EGR turbocharger that drives the turbine and compresses the intake air with a compressor coaxial with the turbine and guides it to the upstream side of the supercharging system of the intake system, and bypasses the turbine of the EGR turbocharger to generate EGR gas. A bypass line for flowing and a bypass valve for opening and closing the bypass line are provided. Than is.

  Thus, in the uppermost turbocharger of the exhaust system in a high speed rotation region, etc., the nozzle opening of the turbine is narrowed down to increase the pressure of the exhaust manifold, and the pressure difference between the exhaust side and the intake side in a relatively high pressure region. If the exhaust gas recirculation is performed while securing the intake air, it becomes possible to recirculate the EGR gas at a high EGR rate even if the intake air is supercharged by the supercharging system, but intake (fresh air) is difficult to enter. As a result, there is a risk that the amount of intake air necessary for combustion will be insufficient.

  At this time, instead of narrowing down the EGR valve, when the bypass valve is closed and the EGR gas flowing through the EGR line is guided to the turbine of the EGR turbocharger, the energy of the EGR gas is recovered by the turbine, and thereby, the EGR gas is coaxial with the turbine. The compressor is driven to compress the intake air, and the intake air whose pressure is increased to the atmospheric pressure or higher is led to the supercharging system to be supercharged.

  In other words, since the intake air whose pressure has already been increased is guided to the supercharging system and further supercharged, the intake air is increased to a pressure higher than that when the intake air taken in from the atmosphere is boosted only by the supercharging system. In addition, the EGR gas works with the turbine of the turbocharger for EGR, so that it can pass through resistance and obtain a narrowing effect, so that the amount of intake air necessary for combustion is insufficient. Excessive EGR gas recirculation is remarkably corrected, and intake air is more easily taken into the engine than before, so that it is possible to secure the amount of intake air necessary for combustion without causing an extreme increase in exhaust pressure. Become.

  In the present invention, a high-pressure stage turbocharger that operates a high-pressure stage turbine with exhaust gas delivered from the engine and supplies intake air compressed by a high-pressure stage compressor to the engine, and a high-pressure stage turbine of the high-pressure stage turbocharger The high-pressure stage turbocharger is constituted by a two-stage supercharging system comprising a low-pressure stage turbocharger that operates a low-pressure stage turbine with exhaust gas delivered from the exhaust gas and feeds the intake air compressed by the low-pressure stage compressor to the high-pressure stage compressor. May be a variable nozzle turbo.

  According to the exhaust loss recovery apparatus of the present invention described above, exhaust gas recirculation is achieved at a high EGR rate while supercharging is performed by a supercharging system, and the amount of intake air necessary for combustion is increased extremely. Since it can be secured without incurring, it is possible to avoid an extreme situation in which the exhaust pressure of the engine is significantly higher than the boost pressure, thereby significantly reducing the pumping loss of the engine and reducing the fuel consumption. It is possible to achieve an excellent effect that a significant improvement can be achieved.

It is the schematic which shows an example of the form which implements this invention. It is the schematic which shows a prior art example.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an example of an embodiment for carrying out the present invention, and parts denoted by the same reference numerals as those in FIG. 2 represent the same items.

  In the present embodiment, the supercharging system constituted by the single-stage turbocharger 2 in the conventional example of FIG. 2 described above is operated by operating the high-pressure turbine 14b with the exhaust gas 8 delivered from the engine 1, and the high-pressure stage. A high-pressure stage turbocharger 14 that feeds the intake air 4 compressed by the compressor 14a to the engine 1, and a low-pressure stage turbine 15b that is operated by the exhaust gas 8 that is sent from the high-pressure stage turbine 14b of the high-pressure stage turbocharger 14 A case where a two-stage supercharging system is illustrated by a low-pressure stage turbocharger 15 that feeds the intake air 4 compressed by the compressor 15a to the high-pressure stage compressor 14a is illustrated. In the example shown here, The high-pressure stage turbocharger 14 constituting the most upstream turbocharger of the system is a high-pressure stage turbine 14b. And it is configured to cheat opening as an adjustable variable-geometry turbocharger.

  In the middle of the EGR line 11 through which the EGR gas 8 ′ flows, the turbine 16b is driven by the EGR gas 8 ′ flowing through the EGR line 11, and the intake air 4 taken in from the air cleaner 17 is compressed by the compressor 16a coaxial with the turbine 16b. And an EGR turbocharger 16 that is led to the air cleaner 3 via the connecting pipe 18 and a bypass line 19 that bypasses the turbine 16b of the EGR turbocharger 16 and flows the EGR gas 8 '; A bypass valve 20 for opening and closing the bypass line 19 is provided.

  Thus, the nozzle opening of the high-pressure turbine 14b in the high-pressure turbocharger 14 is narrowed down in the high-speed rotation region or the like to increase the pressure of the exhaust manifold 9, and the pressure difference between the exhaust side and the intake side in a relatively high pressure region. When the exhaust gas recirculation is performed while ensuring the above, it is possible to recirculate the EGR gas 8 'at a high EGR rate even if the intake air 4 is supercharged by the high pressure turbocharger 14 and the low pressure turbocharger 15. However, the intake air 4 (fresh air) becomes difficult to enter and there is a risk that the intake air 4 necessary for combustion will be insufficient in quantity.

  At this time, when the EGR gas 8 ′ flowing through the EGR line 11 is led to the turbine 16b of the EGR turbocharger 16 instead of narrowing down the EGR valve 12, the energy of the EGR gas 8 ′ is obtained by the turbine 16b. Then, the compressor 16a coaxial with the turbine 16b is driven to compress the intake air 4, and the intake air 4 whose pressure is increased to the atmospheric pressure or higher is supplied to the low pressure compressor 15a of the low pressure turbocharger 15 via the air cleaner 3. It will be led and supercharged.

  That is, since the intake air 4 whose pressure has already been increased is led to the low-pressure stage turbocharger 15 and the high-pressure stage turbocharger 14 and further supercharged, only the low-pressure stage turbocharger 15 and the high-pressure stage turbocharger 14 are used. It is possible to supercharge the intake air 4 to a pressure higher than that when the intake air 4 taken in from the atmosphere is boosted, and the EGR gas 8 'works in the turbine 16b of the EGR turbocharger 16, thereby reducing the passage resistance. Therefore, since the throttle effect is also obtained, the excessive recirculation of the EGR gas 8 ′ which causes the amount of the intake air 4 necessary for combustion to be insufficient is significantly corrected, and the intake air 4 is taken into the engine 1 more than before. Therefore, the amount of intake air 4 necessary for combustion can be ensured without causing an extreme increase in exhaust pressure.

  Therefore, according to the above embodiment, the exhaust gas recirculation is achieved at a high EGR rate while supercharging is performed by the low pressure turbocharger 15 and the high pressure turbocharger 14, and the amount of the intake air 4 necessary for combustion is extremely reduced. Since it can be ensured without causing an increase in the exhaust pressure, an extreme state in which the exhaust pressure of the engine 1 becomes significantly higher than the supercharging pressure can be avoided in advance, whereby the pumping of the engine 1 can be avoided. Loss can be significantly reduced and fuel efficiency can be greatly improved.

  The exhaust loss recovery device of the present invention is not limited to the above-described embodiment. The supercharging system may be configured by a single-stage turbocharger, and further, a turbocharger having three or more stages. Of course, various modifications may be made without departing from the scope of the present invention.

1 Engine 4 Intake 7 Intake manifold 8 Exhaust gas 8 'EGR gas 9 Exhaust manifold 10 Exhaust pipe 11 EGR line 12 EGR valve 14 High-pressure stage turbocharger (supercharging system: variable nozzle turbo)
14a High-pressure stage compressor 14b High-pressure stage turbine 15 Low-pressure stage turbocharger (supercharging system)
15a Low pressure stage compressor 15b Low pressure stage turbine 16 EGR turbocharger 16a Compressor 16b Turbine 19 Bypass line 20 Bypass valve

Claims (2)

  A turbocharger consisting of an appropriate number of turbochargers and at least the most upstream turbocharger of the exhaust system is a variable nozzle turbo capable of adjusting the nozzle opening of the turbine, and is connected between the exhaust manifold and the intake manifold. An exhaust loss recovery device for applying to an engine having an EGR line that recirculates a part of the exhaust gas as EGR gas from the exhaust side to the intake side, and driving the turbine by the EGR gas flowing through the EGR line And an EGR turbocharger that compresses intake air by a compressor coaxial with the turbine and guides it to the upstream side of the supercharging system of the intake system, and a bypass line that bypasses the turbine of the EGR turbocharger and flows EGR gas And an exhaust loss circuit characterized by comprising a bypass valve for opening and closing the bypass line. Apparatus.   The high-pressure stage turbocharger that operates the high-pressure stage turbine with exhaust gas delivered from the engine and supplies the intake air compressed by the high-pressure stage compressor to the engine, and the exhaust gas delivered from the high-pressure stage turbine of the high-pressure stage turbocharger The supercharging system is configured in two stages with a low-pressure stage turbocharger that operates the low-pressure stage turbine and feeds the intake air compressed by the low-pressure stage compressor to the high-pressure stage compressor, and the high-pressure stage turbocharger is a variable nozzle turbo. The exhaust loss recovery device according to claim 1.

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