JP2005054710A - Exhaust gas recirculation device for turbo compound engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compatibly attain improved output and fuel consumption of a turbo compound engine and lower exhaust emission thereof. <P>SOLUTION: An exhaust manifold 18 and an intake manifold 8 are parted for every first cylinder group 14 and every second cylinder group 16, respectively, with their exhaust strokes avoided from overlapping each other. An first exhaust manifold 20 and a second intake manifold 17 belonging to different cylinder groups are communicated with each other via an EGR passage 28, and a second exhaust manifold 21 and a first intake manifold 15 belonging to different cylinder groups are communicated with each other via an EGR passage 25. Thus, smoothing due to the interference of exhaust pulses with intake pulses between the cylinder groups is suppressed and the phase of the exhaust pulses is matched to that of the intake pulses, therefore permitting efficient reflux of exhaust gas and efficient transmission of exhaust energy to a high pressure turbine 19, improving the output of the high pressure turbine 19 and increasing the turbo charging effects of a turbo charger 11 on intake air. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technology for simultaneously improving engine output and fuel consumption and reducing exhaust pollution in an exhaust gas recirculation device provided in a turbo compound engine.

  Conventionally, a turbo compound engine as described in Japanese Patent Application Laid-Open No. 9-2222026 (Patent Document 1) has been proposed. Such a turbo compound engine has a turbocharger and an exhaust energy recovery device. The turbocharger is configured to include a turbine provided in the exhaust system and a compressor connected to the turbine and provided in the intake system. When the turbine is rotated by exhaust, the compressor is rotated and the engine is rotated. Supercharge the intake air. The exhaust energy recovery device further includes a turbine in an exhaust system downstream of the turbocharger, and transmits the rotational force of the turbine that is rotated by exhaust gas to the output shaft of the engine. As a result, the turbo compound engine has improved output and fuel efficiency.

There is also known an exhaust gas recirculation device that reduces nitrogen oxides in exhaust gas by returning a part of engine exhaust gas to an intake manifold and reducing the combustion temperature as a kind of inert gas.
JP-A-9-2222026

  By the way, since the exhaust gas recirculation device is configured to recirculate a part of the exhaust gas to the intake system using the pressure difference between the exhaust manifold and the intake manifold, when the exhaust gas recirculation device is provided in the turbo compound engine, There was a problem like this. That is, when the efficiency of the turbocharger is high, the pressure in the intake manifold becomes higher than the pressure in the exhaust manifold, and the exhaust cannot be recirculated to the intake system.

Moreover, in a turbo compound engine, since the exhaust gas passes through a plurality of turbines, the back pressure of the engine becomes high. As a result, the pumping loss is increased, and there is a problem that the output and the fuel consumption are lowered particularly at a low load.
SUMMARY OF THE INVENTION In view of the above-described conventional problems, the present invention has an object to provide an exhaust gas recirculation device for a turbo-compound engine that simultaneously realizes an improvement in engine output and fuel consumption and a low emission pollution. And

  Therefore, the invention according to claim 1 has a turbocharger that supercharges intake air by exhaust energy, and recovers exhaust energy by rotating the low-pressure turbine by exhaust after passing through the high-pressure turbine of the turbocharger. In the multi-cylinder turbo compound engine, the exhaust manifold and the intake manifold are divided into at least cylinder groups in which the exhaust strokes do not overlap each other, and the exhaust manifolds and the intake manifolds belonging to different cylinder groups are separated through an exhaust recirculation passage. Each of them is characterized by communication.

The invention according to claim 2 includes: a variable throttle valve that increases or decreases a cross-sectional area of the exhaust gas recirculation passage; and a control unit that controls the operation of the variable throttle valve based on an operating state of the engine. It is characterized by.
The invention according to claim 3 is characterized in that the control means controls the operation of the variable throttle valve based on the rotational speed and load of the engine.

  According to a fourth aspect of the present invention, there is provided cooling means for cooling the exhaust gas flowing through the exhaust gas recirculation passage.

  According to the first aspect of the present invention, the exhaust discharged from each cylinder of the turbo compound engine is collected for each cylinder group in which the exhaust strokes do not overlap, and is supplied to the high-pressure turbine of the turbocharger. Since a part of the collected exhaust gas is returned to the intake manifolds belonging to different cylinder groups, smoothing of exhaust pulses and intake pulses due to interference between the cylinder groups is suppressed. In addition, since the phases of the exhaust pulse and the intake pulse match, exhaust recirculation is efficiently performed, the combustion temperature of the engine is lowered, and nitrogen oxides in the exhaust can be reduced. Further, since smoothing of the exhaust pulse is suppressed, the exhaust energy is efficiently transmitted to the high pressure turbine, and the output of the high pressure turbine is improved. Thereby, the supercharging effect by a turbocharger can improve, and an engine output and fuel consumption can be improved.

According to the second aspect of the invention, since the cross-sectional area of the exhaust gas recirculation passage increases or decreases based on the operating state of the engine, optimal exhaust gas recirculation can be performed.
According to the third aspect of the invention, since the variable throttle valve operation control is performed based on the engine speed and load, the exhaust gas recirculation using the sensor provided for engine control and the like is utilized. Can be controlled.

  According to the fourth aspect of the present invention, the exhaust gas flowing through the exhaust gas recirculation passage is cooled, so that the exhaust gas is cooled to return to the intake air of the engine. Thereby, since the combustion temperature of an engine falls more, the nitrogen oxide in exhaust_gas | exhaustion can be reduced more.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a configuration diagram in which the present invention is applied to a 6-cylinder turbo compound engine.
A turbo compound engine (hereinafter referred to as an engine) 1 has an energy recovery device 2. The energy recovery device 2 includes a low-pressure turbine 3, a speed reduction device 4, and a fluid coupling 5. The low-pressure turbine 3 is interposed in the exhaust pipe 6 of the engine 1 and rotates by the exhaust gas that passes through the exhaust pipe 6. The reduction gear 4 reduces the rotation of the low pressure turbine 3. The fluid coupling 5 transmits a rotational force from the speed reduction device 4 to the output shaft 7 of the engine 1 while absorbing a relative displacement between the output shaft 7 of the engine 1 and the speed reduction device 4 due to a rotational fluctuation of the engine 1. Thereby, the energy recovery device 2 can improve the energy efficiency of the engine 1 by recovering the exhaust energy and using it for the rotational energy of the engine 1.

  An intake pipe 9 is connected to an intake port of the engine 1 via an intake manifold 8. An air cleaner 10 that removes impurities such as dust from the outside air, a compressor 12 that constitutes a turbocharger 11, and an intercooler 13 that cools the intake air are interposed in the intake pipe 9 from upstream. The intake manifold 8 includes a first intake manifold 15 connected to an intake port of a first cylinder group 14 composed of cylinders (# 1, # 2, # 3) that do not overlap in the exhaust stroke, and a first cylinder A second intake manifold 17 connected to an intake port of a second cylinder group 16 constituted by cylinders (# 4, # 5, # 6) other than the group 14 is divided into two.

  On the other hand, a high pressure turbine 19 constituting the turbocharger 11 is connected to an exhaust port of the engine 1 via an exhaust manifold 18. There are two exhaust manifolds 18, a first exhaust manifold 20 connected to the exhaust port of the first cylinder group 14 and a second exhaust manifold 21 connected to the exhaust port of the second cylinder group 16. It is divided into The intake manifold 15 and the exhaust manifold 18 may be integrated as long as the inside thereof is divided into two for each cylinder group that does not overlap the exhaust stroke. The high-pressure turbine 19 is connected to an exhaust pipe 6 in which the low-pressure turbine 3 is interposed. Further, a muffler 22 that silences the exhaust is interposed downstream of the low-pressure turbine 3.

  The first intake manifold 15 and the second exhaust manifold 21 communicate with each other by an EGR passage 25 (exhaust gas recirculation passage) through an EGR valve 23 (variable throttle valve) and an EGR cooler 24 (cooling means). The second intake manifold 17 and the first exhaust manifold 20 are communicated with each other by an EGR passage 28 (exhaust gas recirculation passage) including an EGR valve 26 (variable throttle valve) and an EGR cooler 27 (cooling means). Yes. The EGR valves 23 and 26 increase or decrease the flow passage cross-sectional areas of the EGR passages 25 and 28 based on a signal from a controller 31 (control means) incorporating a microcomputer.

  The engine 1 is provided with a rotation speed sensor 32 that detects a rotation speed and a load sensor 33 that detects a load such as a fuel supply amount, an intake air flow rate, or an intake negative pressure. The controller 31 inputs the rotational speed and load of the engine 1 from the rotational speed sensor 32 and the load sensor 33, calculates the EGR flow rate, and duty-controls the EGR valves 23 and 26 based on the EGR flow rate. The EGR flow rate is calculated by storing a map in which the controller 31 has previously set the EGR flow rate corresponding to the rotational speed and load of the engine 1 and corresponding to the rotational speed and load of the engine 1 from this map. This is done by reading the EGR flow rate.

Next, the operation of the exhaust gas recirculation device of the engine 1 will be described.
Exhaust gas discharged from each exhaust port of the engine 1 passes through the first exhaust manifold 20 or the second exhaust manifold 21 and is supplied to the high-pressure turbine 19. The high-pressure turbine 19 is rotated by these exhausts, and the compressor 12 is driven to rotate.
The exhaust gas that has passed through the high-pressure turbine 19 passes through the low-pressure turbine 3 and then passes through the muffler 22 and is released into the atmosphere. The low pressure turbine 3 is rotationally driven by this exhaust. The rotation of the low-pressure turbine 3 is decelerated by the speed reducer 4 and is transmitted to the output shaft 7 of the engine 1 through the fluid coupling 5 while absorbing rotational fluctuations of the engine 1. Thereby, since the exhaust energy of the engine 1 is recovered and used for the rotational energy of the engine 1, the output and fuel consumption of the engine 1 are improved.

  On the other hand, the outside air sucked into the air cleaner 10 is compressed by the compressor 12 after impurities such as dust are removed by the air cleaner 10 as intake air of the engine 1. Although this compressed intake air becomes high temperature, it is cooled by passing through the intercooler 13. Thereby, the volume of the intake air is reduced and the intake efficiency of the engine 1 is improved. The intake air cooled by the intercooler 13 passes through the first intake manifold 15 or the second intake manifold 17 and is supplied to each cylinder of the engine 1.

  The first exhaust manifold 20 and the second intake manifold 17 belonging to different cylinder groups are communicated with each other via the EGR passage 28, and the second exhaust manifold 21 and the first intake manifold 15 belonging to different cylinder groups are connected to each other. Since the communication is made via the EGR passage 25, a part of the exhaust that passes through the first exhaust manifold 20 passes through the EGR passage 28 and is returned to the second intake manifold 17, while the second exhaust Part of the exhaust gas that passes through the manifold 21 passes through the EGR passage 25 and is returned to the first intake manifold 15. As a result, the smoothing of the exhaust pulse and the intake pulse due to interference between the cylinder groups is suppressed, and as shown in FIG. 2, the phases of the exhaust pulse and the intake pulse match, so that the exhaust pressure and the intake pressure Is utilized to the maximum, and exhaust gas recirculation is performed efficiently. Therefore, the combustion temperature of the engine 1 can be further reduced, and nitrogen oxides in the exhaust can be reduced. Further, since smoothing of the exhaust pulse is suppressed, the exhaust energy is efficiently transmitted to the high pressure turbine 19 and the output of the high pressure turbine 19 is improved. Thereby, the supercharging effect of the intake air by the turbocharger 11 is enhanced, and the output of the engine 1 is improved.

Further, the controller 31 controls the operation of the EGR valve 23 and the EGR valve 26 based on the rotational speed and load of the engine 1 detected by the rotational speed sensor 32 and the load sensor 33, respectively. Thereby, the optimal exhaust gas recirculation can be performed by using a sensor provided for controlling the engine 1 and the like.
Further, since the EGR passages 25 and 28 are provided with the EGR coolers 24 and 29, respectively, the exhaust gas passing through the EGR passages 25 and 28 is cooled, the temperature of the intake air to the engine 1 is further lowered, and the combustion temperature of the engine 1 is reduced. Can be further reduced.

In the present embodiment, the case where the engine 1 has six cylinders has been described. However, the present invention is not limited to this, and the engine 1 has a plurality of cylinders and is divided into a plurality of cylinder groups in which exhaust strokes do not overlap. If possible, it can be implemented in the same manner.
Further, in this embodiment, the exhaust manifold 18 and the intake manifold 8 are each divided into two. However, if the exhaust manifold 18 and the intake manifold 8 are divided for each cylinder group where the exhaust strokes do not overlap, the same can be implemented even if divided into three or more.

The block diagram of the exhaust gas recirculation apparatus of the turbo compound engine in the Example of this invention Timing chart showing the exhaust and intake pulses of a 6-cylinder turbo compound engine

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Turbo compound engine 3 Low pressure turbine 8 Intake manifold 11 Turbocharger 15 1st intake manifold 17 2nd intake manifold 18 Exhaust manifold 19 High pressure turbine 20 1st exhaust manifold 21 2nd exhaust manifold 23, 26 EGR valve 24, 27 EGR cooler 25, 28 EGR passage 31 Controller

Claims (4)

In a multi-cylinder turbo compound engine having a turbocharger that supercharges intake air by exhaust energy and recovering exhaust energy by rotating the low-pressure turbine by exhaust after passing through the high-pressure turbine of the turbocharger,
Divide the exhaust manifold and intake manifold into cylinder groups that do not overlap in the exhaust stroke.
An exhaust gas recirculation apparatus for a turbo compound engine, wherein an exhaust manifold and an intake manifold belonging to different cylinder groups are communicated with each other via an exhaust gas recirculation passage. A variable throttle valve that increases or decreases the cross-sectional area of the exhaust gas recirculation passage;
Control means for controlling the operation of the variable throttle valve based on the operating state of the engine;
The exhaust gas recirculation device for a turbo compound engine according to claim 1, wherein   3. The exhaust gas recirculation apparatus for a turbo compound engine according to claim 2, wherein the control means controls the operation of the variable throttle valve based on a rotation speed and a load of the engine.   The exhaust gas recirculation device for a turbo compound engine according to any one of claims 1 to 3, further comprising cooling means for cooling the exhaust gas flowing through the exhaust gas recirculation passage.

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