JP2009115089A - Engine with supercharger and its operating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simultaneously achieve both a high exhaust gas recirculation ratio and high filling pressure in all engine load regions, in an engine 1 with superchargers having an exhaust turbo-supercharger 6 with a turbine 6a and a first compressor 6b and a mechanical supercharger 7 with a second compressor. <P>SOLUTION: The engine 1 is provided with an exhaust gas recirculation system 10 having a recirculation passage 11 branched from the downstream side of the turbine 6a in an exhaust pipe 4 and opened on the upstream side of the second compressor (mechanical supercharger 7) in an intake pipe 2 and with a throttle valve 12 arranged in either a position on the upstream side at the opening point of the recirculation passage 11 in the intake pipe 2 or a position on the downstream side at the branch point of the recirculation passage 11 in the exhaust pipe 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a supercharged engine. More specifically, an intake pipe for supplying fresh air or a new mixture to the cylinder, an exhaust pipe for exhausting exhaust gas from the cylinder, a turbine disposed in the exhaust pipe, and the intake pipe An exhaust turbocharger having a first compressor disposed therein, and a mechanical supercharger having a second compressor disposed upstream of the first compressor in the intake pipe, A supercharger including a first bypass passage in which a closing element is disposed and branched from the upstream side of the second compressor in the intake pipe and reconnected to the downstream side of the second compressor in the intake pipe Related to the engine. The invention also relates to a method for operating a supercharged engine of the type described above.

  As used herein, the term engine includes a spark ignition engine, a hybrid drive system or hybrid vehicle engine, or a diesel engine.

  In general, to supercharge an engine, the compressor and turbine are placed on the same shaft shaft and a hot exhaust gas stream is supplied to the turbine and expanded to release energy in the turbine, resulting in the shaft. An exhaust turbocharger is used to rotate the engine. The energy transferred from the exhaust stream to the turbine and ultimately to the shaft is utilized to drive a compressor similarly disposed on the shaft. The compressor compresses the charge air supplied thereto, so that supercharging of the charge air to the cylinder is obtained.

  In addition, as described above, in order to supercharge the engine, unlike the exhaust turbocharger that uses the exhaust energy of hot exhaust gas, a mechanical supercharger that takes the energy required for driving from the engine itself. A machine may be used. In either case, an intercooler may be provided to cool the filled air (see, for example, Patent Documents 1 and 2).

The supercharging first serves to increase the engine output. That is, the air required for the combustion process is compressed, so that more mass of air can be supplied to each cylinder per work cycle. In this way, the fuel mass and the average effective pressure p _me can be increased.

  Therefore, supercharging is an appropriate means for increasing the engine output without changing the displacement (stroke volume), or for reducing the displacement without changing the magnitude of the output. In any case, supercharging improves specific performance. When the vehicle is in a given transient state, the total load can be changed to an inherent lower consumption. As a result, supercharging promotes a reduction in engine fuel consumption, i.e. an improvement in engine efficiency.

A further basic purpose of a turbocharged engine is to reduce pollutant emissions. Engine supercharging can also be a means to solve this problem. In particular, in the case of a supercharge of the targeted design, it is possible to gain an advantage in efficiency and exhaust emissions. Thus, with appropriate supercharging, for example in diesel engines, nitrogen oxides can be reduced without loss of efficiency. At the same time, it may have an effective impact on hydrocarbon emissions. Similarly, carbon dioxide emissions that are directly related to fuel consumption are also reduced as fuel consumption decreases. Therefore, supercharging is also suitable for reducing pollutant emissions.
JP-A-9-242549 Special table 2008-537053 gazette

  A further object of the development of a supercharged engine is to improve the response characteristics in the dynamic operation of the engine and to improve the torque characteristics in the low speed region.

  Specifically, in the prior art, a perceptible torque decrease is observed when the rotational speed is lower than a predetermined rotational speed. This result is undesirable and is one of the most important drawbacks of an exhaust turbocharger.

  If one considers that the filling pressure depends on the turbine pressure ratio, the above torque drop can be understood. For example, in a diesel engine, if the engine speed is reduced, this results in a reduction in exhaust mass flow and, as a result, a reduction in turbine pressure ratio. This results in a decrease in filling pressure, which is synonymous with a decrease in torque, as the speed decreases.

  Here, a decrease in the filling pressure can be basically dealt with by reducing the size of the cross-sectional area of the turbine accompanied by an increase in the turbine pressure ratio, but this causes a disadvantage at a high rotation speed.

  In order to improve torque characteristics, a plurality of turbochargers or a combination of an exhaust turbocharger and a mechanical supercharger is often used. An engine provided with the above-described mechanical supercharger in addition to the exhaust turbocharger is also the subject of the present invention.

  However, further measures may be required to meet future regulations regarding pollutant emissions. The focus here is specifically on reducing nitrogen oxide emissions associated with diesel engines. Since the formation of nitrogen oxides requires not only excess air but also high temperatures, one of the concepts for reducing nitrogen oxides is to improve the combustion process or to use a relatively low combustion temperature It is.

The means here is exhaust gas recirculation (EGR), that is, recirculation of the combustion gas exiting the exhaust pipe and entering the intake pipe, thereby providing an exhaust gas recirculation rate (EGR rate). As the amount of nitrogen increases, the emission of nitrogen oxides can be greatly reduced. Here, the exhaust gas recirculation rate x _EGR is defined by the following equation (1).

x _EGR = m _EGR / (m _EGR + m _{Fresh air} ) (1)
Here, m _EGR represents the mass of recirculated exhaust gas, and m _{Fresh air} represents the mass of supplied air, preferably compressed fresh air or charged air.

  Exhaust gas recirculation is also suitable for reducing unburned hydrocarbon emissions in the partial load region.

To obtain a significant reduction in nitrogen oxides, a high exhaust gas recirculation rate with x _EGR of 60% to 70% is required.

  When using exhaust gas recirculation and exhaust turbocharging at the same time according to the prior art, in the conventional concept, the recirculated exhaust gas is drawn from the exhaust pipe upstream of the turbine and cannot be used to drive the turbine As such, there will necessarily be interference between the objectives of exhaust gas recirculation and exhaust turbocharging. Recirculation of exhaust gas exiting the exhaust pipe and entering the intake pipe requires a differential pressure, in other words, a pressure gradient from the exhaust side to the intake side. In order to obtain a high EGR rate, a corresponding high pressure gradient is required.

  For this reason, in the prior art, the exhaust gas recirculation passage, i.e., the recirculation passage, ensures that the exhaust back pressure in the exhaust pipe is reliably higher than the filling pressure in the intake pipe. Branching from the upstream side of the turbine of the tube results in the required pressure gradient.

  In contrast to this prior art, the object of the present invention is to overcome the disadvantages of the prior art in a turbocharged engine as described above, and to achieve a high exhaust gas recirculation rate and a high filling pressure in all engine load regions. It aims at providing the engine with a supercharger which can implement | achieve simultaneously.

  A further object of the present invention is to clarify a method for operating the above-described supercharged engine.

  A first object of the present invention is to provide an intake pipe for supplying fresh air or a new mixture to a cylinder, an exhaust pipe for exhausting exhaust gas from the cylinder, and a turbine disposed in the exhaust pipe. An exhaust turbocharger having a first compressor disposed in the intake pipe and a mechanical supercharger having a second compressor disposed upstream of the first compressor in the intake pipe And a first bypass passage branching from the upstream side of the second compressor in the intake pipe and reconnected to the downstream side of the second compressor in the intake pipe. In an engine with a supercharger, an exhaust gas recirculation system having a recirculation passage that branches from a downstream side of the turbine in the exhaust pipe and opens to an upstream side of the second compressor in the intake pipe, and the intake pipe Opening of the recirculation passage in And a throttle valve disposed at a position on either the upstream side of the exhaust pipe or the downstream side of the branch point of the recirculation passage in the exhaust pipe. The

  The engine according to the present invention is equipped with a so-called low-pressure EGR system, that is, an EGR system of a type in which exhaust gas is drawn not from the upstream side of the turbine but from the downstream side in exhaust gas recirculation.

  This has a significant advantage over conventional engines in that the recirculated exhaust gas flows through the turbine before it is recirculated to the intake pipe, thereby being used to drive the turbine. In this respect, the intended interference between exhaust gas recirculation and exhaust turbocharging is solved. This is because a high EGR rate, i.e. exhaust gas recirculated in large quantities, does not result in a reduction in turbine pressure ratio or pressure ratio in the compressor, and therefore no reduction in torque availability.

  The engine according to the invention recirculates a large amount of exhaust gas and at the same time produces or supplies a sufficiently high filling pressure, which has a great effect on improving the operating characteristics of the engine, especially in the partial load region.

  A throttle valve is provided to ensure or ensure a pressure gradient (differential pressure) between the exhaust side and the intake side required for exhaust gas recirculation, and this throttle valve is a pressure gradient, that is, an EGR rate. It is a means to adjust.

  The throttle valve may be disposed upstream of the opening point of the recirculation passage in the intake pipe. In this case, the intake pressure can be throttled, that is, reduced by adjusting the throttle valve in the direction of the closed position. In this example, the pressure gradient or EGR rate is increased by reducing the pressure in the intake pipe downstream of the throttle valve.

  On the other hand, the throttle valve may be disposed downstream of the branch point of the recirculation passage in the exhaust pipe. By adjusting the throttle valve in the direction of the closed position, the exhaust back pressure upstream of the throttle valve in the exhaust pipe is affected, in other words, increased. In this example, the pressure gradient or EGR rate is increased by increasing the exhaust pipe back pressure.

  These two embodiments are common in that the EGR rate is controlled or adjusted by a throttle valve. By adjusting the throttle valve in the opening direction or the closing direction, the pressure in the intake pipe or the exhaust back pressure in the exhaust pipe is directly changed, and as a result, the EGR rate is indirectly adjusted or controlled.

  Thus, as the throttle valve is closed, the differential pressure between the exhaust side and the intake side increases, and the EGR rate increases.

  The first bypass passage basically allows fresh air to be supplied to the first compressor of the exhaust turbocharger while bypassing the mechanical supercharger (second compressor). As a result, the first bypass passage makes it possible to supply fresh air directly to the first compressor, thereby realizing a single stage supercharging of the engine.

  On the other hand, the first bypass passage can be controlled by a closing element, in particular affecting the filling pressure at low rotational speeds or at low loads.

  In order to increase the filling pressure, the closing element arranged in the first bypass passage is adjusted in the closing direction. As a result, the mass of air actually supplied and supplied to the engine and the air-fuel ratio λ can be increased.

  Conversely, in order to reduce the filling pressure, the closing element is adjusted in the opening direction, so that more filling air is blown out from the first bypass passage.

  Such an approach is particularly advantageous when a high EGR rate and an increased charge air amount or a high air / fuel ratio λ is performed at low speeds or low and medium loads.

  The compression of the charge air by the second compressor of the mechanical supercharger in the low speed range improves the responsiveness as a result of the mechanical connection of the turbocharger to the engine and the use of torque in the low speed range Improve possibilities.

  If a two-stage compression of charge air is preferred, the closure element in the first bypass passage should be closed.

  Thus, the first compressor may compress the air mass flow pre-compressed by the second compressor under two-stage compression, or it may compress the air mass flow that is not pre-compressed.

  The design of the two compressors depends in particular on the control of the first bypass passage. If the first bypass passage is opened at a relatively high rotational speed or high charge air volume because the mechanical supercharger cannot carry a large amount of air mass, the first compressor will be correspondingly larger Set to dimension.

  The engine according to the invention achieves the first object of the invention as detailed above. Specifically, it is possible to provide a supercharged engine capable of simultaneously satisfying a high exhaust gas recirculation rate and a high filling pressure in all load regions of the engine.

  Further advantageous engine embodiments are described below.

  Implementation comprising a second bypass passage that branches from a position upstream of the first compressor in the intake pipe and reopens at a position downstream of the first compressor, and a closing element provided in the second bypass passage. An engine of the form is advantageous.

  This embodiment allows the first compressor to be bypassed and allows charge air to be supplied to the cylinder without being compressed by the first compressor.

  A third bypass passage is provided for exhausting the exhaust gas from the cylinder to the downstream side of the turbine in the exhaust pipe by bypassing the turbine, and the third bypass passage has an exhaust gas blowing amount to the exhaust pipe. The engine of the embodiment in which a closure element for control is provided is advantageous.

  Designing a turbine as a wastegate turbine can set the size of the turbine cross-sectional area small, in other words, can be configured for a relatively small displacement. If the exhaust mass flow rate exceeds a critical value, a part of the exhaust flow rate as the so-called blow-off amount of the exhaust gas bypasses the turbine through the third bypass passage.

  The smaller the turbine, the lower the inertia, and as a result, the rotor is accelerated and decelerated quickly with a relatively small inertial mass moment. Therefore, the response characteristic of the engine is improved.

  In addition, small turbines are light and have a small mounting space, which allows for a more condensed package in the engine room, and in particular desirable arrangements that bring the turbine closer to the cylinder.

  Advantageously, the engine of the embodiment in which the closing element in the first bypass passage is a valve or a throttle flap.

  Embodiments in which the throttle valve is controllable by electricity, hydraulic, fluid pressure, mechanical or magnetic, preferably by an engine controller, are advantageous.

  An embodiment engine in which the turbine has a variable turbine geometry is advantageous.

  Variable turbine geometry increases supercharge flexibility. As a result, it allows various applications of the turbine geometry to the corresponding engine operating point or current exhaust gas mass flow.

  In particular, the combination of a turbine with a variable turbine geometry and a third bypass passage that bypasses the turbine allows the turbine to be configured for a small exhaust mass, i.e. a partial load region. It makes it possible to obtain a high turbine pressure ratio at low rotation, i.e. a small exhaust mass flow.

  However, the turbine may have a geometry that is essentially fixed and not variable.

  The engine of the embodiment in which an intercooler for cooling the air compressed by the first compressor is disposed downstream of the first compressor in the intake pipe is advantageous. The intercooler lowers the temperature of the air, thereby increasing the density of the intake air flow that is carried, thereby contributing to improved combustion chamber filling.

  The engine of the embodiment in which an intercooler for cooling the air compressed by the second compressor is arranged between the first and second compressors in the intake pipe is advantageous. Such an intercooler is arranged upstream of the opening point of the first bypass passage in the intake pipe so that the mass flow sucked through the first bypass passage, when appropriate, does not pass through the intercooler. preferable.

  The intercooler between the first and second compressors reduces the temperature of the feed stream to increase the density and reduces the volume of flow through the first compressor, assuming the mass flow is the same. As a result, the first compressor can be set to small dimensions, which provides the advantages associated with the small turbine already described above.

  An engine of an embodiment in which the recirculation passage in the exhaust gas recirculation system is provided with a cooler for cooling the exhaust gas flowing through the recirculation passage is advantageous. Such a cooler lowers the temperature of the hot exhaust gas stream, thereby increasing the density of the exhaust gas so that a large mass of exhaust gas can be recirculated. The temperature of the newly charged air generated during the mixing of the fresh air and the recirculated exhaust gas in the intake pipe is lowered, and as a result, the cooler of the recirculation passage contributes to the improvement of the filling of the combustion chamber.

  An embodiment of the engine in which a closure element is provided in the recirculation passage in the exhaust gas recirculation system is advantageous. Such a closing element provides control of the exhaust gas recirculation rate in addition to the throttle valve.

  The closing element of the recirculation passage is particularly advantageous when exhaust gas recirculation is completely suppressed during full load operation of the engine, at which time the closing element is closed.

  A second aspect for achieving the object of the present invention is a method for controlling a supercharged engine of the type described above, in order to increase the amount of recirculated gas, that is, the EGR rate, so that the intake pipe or exhaust gas is increased. A throttle valve disposed in the intake pipe or the exhaust pipe in order to reduce the amount of recirculation gas, that is, the EGR rate, to control the throttle valve disposed in the pipe more closed. And a step of controlling the valve to the more open side.

  In connection with the engine, what has been said above applies equally to the method according to the invention.

  As the engine load increases, a step of opening the throttle valve disposed in the intake pipe or the exhaust pipe more widely, and as the engine load decreases, a throttle valve disposed in the intake pipe or the exhaust pipe is provided. A control method comprising a more closing step is advantageous.

  This embodiment makes it possible to reduce the amount of exhaust gas recirculated as the engine load increases. A high exhaust gas recirculation rate is preferred when the engine is operating at partial load, but at high loads, especially at full load, a small amount of exhaust gas is recirculated, that is, a small amount of exhaust gas recirculation occurs. Is called. For this purpose, the throttle valve is driven as described above, in other words it needs to be opened and closed.

  FIG. 1 shows an embodiment of a supercharged engine 1 comprising five cylinders 3 as an example. The cylinders 3 of this engine 1 are arranged in series.

  An exhaust pipe 4 is provided for exhausting hot exhaust gas from the cylinder 3. The engine 1 also includes an intake pipe 2 for supplying new air or a new air-fuel mixture to the cylinder 3.

  The engine 1 includes an exhaust turbocharger 6 and a mechanical supercharger 7. The exhaust turbocharger 6 has a turbine 6 a disposed in the exhaust pipe 4 and a first compressor 6 b disposed in the intake pipe 2. The mechanical supercharger 7 has a second compressor disposed on the upstream side of the first compressor 6b in the intake pipe 2. The turbine 6a preferably has a variable turbine geometry.

  In order to bypass the mechanical supercharger 7 (second compressor), the intake pipe 2 branches from the upstream side of the mechanical supercharger 7, and the intake pipe 2 is downstream of the mechanical supercharger 7. A first bypass passage 8 that opens again is provided.

  The first bypass passage 8 functions to adjust the filling pressure by blowing the filling air, particularly at a low rotational speed. A closing element 9 is provided therein for opening and closing the first bypass passage 8.

  The fresh air supplied to the cylinder 3 includes a second compressor of the mechanical supercharger 7 that functions as a low-pressure stage, and a first compressor that functions as a high-pressure stage and is disposed on the downstream side of the second compressor. 6b and compressed in two stages. However, with the closure element 9 in the open position, single stage compression is also available.

  Similarly, second and third bypass passages 14 and 16 may be provided to bypass the turbine 6a and the first compressor 6b of the exhaust turbocharger 6, respectively. Closing elements 15, 17 can be arranged in the bypass passages 14, 16, respectively. The second bypass passage 14 branches from the upstream side of the first compressor 6b in the intake pipe 2 (more specifically, between the first compressor 6b in the intake pipe 2 and the opening point of the first bypass passage 8) and The intake pipe 2 opens again downstream of the first compressor 6b. The third bypass passage 16 bypasses the turbine 6a and exhausts the exhaust gas from the cylinder 3 to the downstream side of the turbine 6a in the exhaust pipe 4.

  The intercooler 5 is disposed downstream of the first compressor 6b in the intake pipe 2 and decreases the temperature of the supplied fluid (air compressed by the first compressor 6b) to increase the density.

  An intercooler that cools the air compressed by the second compressor may be disposed between the first compressor 6b and the mechanical supercharger 7 (second compressor) in the intake pipe 2. This intercooler is preferably disposed upstream of the opening point of the first bypass passage 8 in the intake pipe 2.

  The engine 1 shown in FIG. 1 includes a recirculation passage 11 that branches from the downstream side of the turbine 6a in the exhaust pipe 4 and opens to the upstream side of the mechanical supercharger 7 (second compressor) in the intake pipe 2. A low pressure EGR system 10 is provided.

  The recirculation passage 11 is provided with an EGR cooler 13 for cooling the exhaust gas flowing through the recirculation passage.

  The exhaust from the cylinder 3 is drawn from the downstream side of the turbine 6a rather than the upstream side of the turbine 6a in the exhaust pipe 4 as in the prior art, so that the exhaust passes through the turbine 6a before being recirculated. At the same time, it serves to drive the turbine 6a and indirectly drives the first compressor 6b.

  A throttle valve 12 is disposed on the upstream side of the opening point of the recirculation passage 11 in the intake pipe 2. By this throttle valve 12, there is a gap between the exhaust pipe 4 and the intake pipe 2 required for exhaust gas recirculation. The differential pressure changes.

  As the throttle valve 12 is closed, the pressure in the intake pipe 2 on the downstream side of the throttle valve 12 decreases. As a result, the pressure gradient (differential pressure) between the exhaust pipe 4 and the intake pipe 2 increases, and the EGR rate increases. Thus, the throttle valve 12 reduces the pressure in the intake pipe 2 on the downstream side of the throttle valve 12, thereby increasing the pressure gradient and adjusting the EGR rate.

  Therefore, in order to increase the amount of recirculated gas (EGR rate), the throttle valve 12 is controlled to be more closed, and in order to reduce the amount of recirculated gas (EGR rate), the throttle valve 12 is more controlled. Control to open side.

  It is preferable to open the throttle valve 12 more widely as the engine load increases, and to close the throttle valve 12 more as the engine load decreases.

  It is preferable to provide a closing element in the recirculation passage 11 and to control the EGR rate together with the throttle valve 12 by this closing element. In particular, during full load operation of the engine 1, it is preferable to close the closing element of the recirculation passage 11 so that exhaust gas recirculation is completely suppressed.

  FIG. 2 shows a schematic diagram of a second embodiment of the supercharged engine 1. It should be noted that only points different from the embodiment shown in FIG. 1 will be described, and refer to FIG. 1 for other points (the same reference numerals are used for the same components).

  Unlike the embodiment shown in FIG. 1, the throttle valve 12 is disposed in the exhaust pipe 4 in the engine 1 shown in FIG. 2. Specifically, the exhaust pipe 4 is disposed downstream of the branch point of the recirculation passage 11.

  By adjusting the throttle valve 12 in the closing direction, the exhaust back pressure upstream of the throttle valve 12 in the exhaust pipe 4 increases. The pressure gradient required for the exhaust gas recirculation system 10 is increased by increasing the exhaust back pressure in the exhaust pipe 4 by means of the throttle valve 12, thereby increasing the EGR rate.

  Therefore, as in the embodiment shown in FIG. 1, in order to increase the amount of recirculated gas (EGR rate), the throttle valve 12 is controlled to be more closed, and the amount of recirculated gas (EGR rate) is reduced. In order to reduce this, the throttle valve 12 is controlled to be more open.

1 is a schematic diagram showing a first embodiment of an engine according to the present invention. It is the schematic which shows 2nd embodiment of the engine according to this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine with a supercharger 2 Intake pipe 3 Cylinder 4 Exhaust pipe 5 Intercooler 6 Exhaust turbo supercharger 6a Turbine 6b First compressor 7 Mechanical supercharger (second compressor)
8 First bypass passage 9 Closed casting element 10 Exhaust gas recirculation system 11 Recirculation passage 12 Throttle valve 13 EGR cooler 14 Second bypass passage 15 Closing element 16 Third bypass passage 17 Closing element

Claims (10)

An intake pipe for supplying fresh air or a new air-fuel mixture to the cylinder;
An exhaust pipe for exhausting exhaust gas from the cylinder;
An exhaust turbocharger having a turbine disposed in the exhaust pipe and a first compressor disposed in the intake pipe;
A mechanical supercharger having a second compressor disposed upstream of the first compressor in the intake pipe;
A supercharger comprising a first bypass passage in which a closing element is disposed and branched from the upstream side of the second compressor in the intake pipe and reconnected to the downstream side of the second compressor in the intake pipe In the attached engine,
An exhaust gas recirculation system having a recirculation passage which branches from the downstream side of the turbine in the exhaust pipe and opens to the upstream side of the second compressor in the intake pipe;
A throttle valve disposed at a position upstream of the opening point of the recirculation passage in the intake pipe or downstream of the branch point of the recirculation passage in the exhaust pipe. An engine with a supercharger. A second bypass passage is provided that branches from the upstream side of the first compressor in the intake pipe and opens again on the downstream side of the first compressor in the intake pipe;
A closing element is disposed in the second bypass passage;
The engine with a supercharger according to claim 1. A third bypass passage is provided for exhausting the exhaust gas from the cylinder to the downstream side of the turbine in the exhaust pipe, bypassing the turbine;
The third bypass passage is provided with a closing element for controlling the amount of exhaust gas blown into the exhaust pipe.
The engine with a supercharger according to claim 1 or 2. The turbine has a variable turbine geometry,
The engine with a supercharger according to any one of claims 1 to 3. An intercooler for cooling the air compressed by the first compressor is disposed downstream of the first compressor in the intake pipe.
The supercharged engine according to any one of claims 1 to 4. An intercooler for cooling the air compressed by the second compressor is disposed between the first and second compressors in the intake pipe.
The supercharged engine according to any one of claims 1 to 5. The recirculation passage in the exhaust gas recirculation system is provided with a cooler that cools the exhaust gas flowing through the recirculation passage.
The supercharged engine according to any one of claims 1 to 6. A closure element is provided in the recirculation passage in the exhaust gas recirculation system;
The supercharged engine according to any one of claims 1 to 7. A method for operating a supercharged engine according to any one of claims 1 to 8,
Controlling the throttle valve disposed in the intake pipe or the exhaust pipe to be more closed in order to increase the amount of recirculation gas through the recirculation passage;
A method of operating the engine with a supercharger, including a step of controlling the throttle valve disposed in the intake pipe or the exhaust pipe to be more open in order to reduce the amount of recirculated gas through the recirculation passage. . Opening the throttle valve disposed in the intake pipe or the exhaust pipe more widely as the engine load increases;
The supercharger-equipped engine operating method according to claim 9, further comprising: closing a throttle valve disposed in the intake pipe or the exhaust pipe as the engine load decreases.

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