EP1728988A1 - System and method for charging an engine - Google Patents

Abstract

The engine has a supply duct (32) conveying a mixture containing air and a recycled exhaust gas from a pressure wave surcharger (2) to a combustion chamber of an internal combustion engine (1). An exhaust gas outlet duct (42) evacuates the exhaust gas from the surcharger. A supply duct (33) conveys another mixture containing air and a recycled exhaust gas from the surcharger to the combustion chamber. An exhaust gas outlet duct (43) evacuates the exhaust gas from the surcharger. The ducts (42, 43) comprise butterfly valves (44, 45) controlled by an electronic control unit (5). An independent claim is also included for an internal combustion engine supplying method.

Description

The invention relates to exhaust gas recirculation systems or EGR systems (Exhaust Gas Recirculation) associated with internal combustion engines in motor vehicles.

These systems make it possible to take a part of the exhaust gas and reinject the part taken from the engine air intake circuit.

These recirculation systems make it possible to recycle a portion of the exhaust gases and to reduce the amount of nitrogen oxides emitted by the engine.

Some EGR systems include a Pressure Wave Surge (PWS) compressor. This compressor consists of a rotor comprising one or more channel layers. The rotor extends between the exhaust circuit and the intake circuit and is arranged so that during the rotation of the rotor, the channels are sequentially in communication with the exhaust circuit and the circuit. admission. The pressure difference between the two circuits causes a shock wave inside each channel of the rotor. The exhaust gas compresses the fresh gases and the mixture of air and exhaust gas is injected to the engine.

The pressure wave compressor has the particularity that it provides both an engine boost function and a recirculation function of the exhaust gas.

However, the rate of recycled gas must be precisely controlled. In particular, the rate of gases recycled in the admitted gases must not exceed a maximum limit beyond which fuel combustion would be difficult or incomplete, with the risk of producing polluting particles.

The document US 4,517,950 discloses a method and apparatus for controlling the exhaust gas recirculation rate in a PWS as a function of engine load conditions. Butterfly valves are used to adjust the flow in the low pressure line of the circuit air intake and / or in the low pressure conduit of the exhaust gas circuit.

Moreover, in the field of EGR systems, solutions have been proposed to improve the combustion of the air-fuel mixture in the engine. These solutions provide for forming fluid layers in the combustion chamber (s) of the engine, which has the effect of spreading the combustion over time.

The document FR 2,852,059 describes a heat engine in which a combustion chamber is fed by two fluid streams each having a rate of recirculated gas regulated by flow control means. The two fluid streams feed the combustion chamber and thus form separate layers of oxidizing fluids with variable and controllable recirculated gas rates.

An object of the invention is to control the recirculation of the exhaust gas and more particularly the formation of fluid layers in the combustion chamber or chambers.

• un premier conduit d'alimentation apte à amener un premier mélange contenant de l'air et des gaz d'échappement recyclés depuis un compresseur à onde de pression jusqu'à une chambre de combustion du moteur,
• un premier conduit de sortie de gaz d'échappement apte à évacuer des gaz d'échappement depuis le compresseur à onde de pression,
  caractérisé en ce qu'il comprend en outre
• un deuxième conduit d'alimentation apte à amener un deuxième mélange contenant de l'air et des gaz d'échappement recyclés depuis le compresseur à onde de pression jusqu'à la chambre de combustion du moteur, et
• un deuxième conduit de sortie de gaz d'échappement apte à évacuer des gaz d'échappement depuis le compresseur à onde de pression.

To this end, the subject of the invention is an engine comprising:

• a first feed duct adapted to supply a first mixture containing air and recycled exhaust gases from a pressure wave compressor to a combustion chamber of the engine,
• a first exhaust gas outlet duct capable of evacuating exhaust gases from the pressure wave compressor,
  characterized in that it further comprises
• a second feed duct adapted to supply a second mixture containing air and recycled exhaust gases from the pressure wave compressor to the combustion chamber of the engine, and
• a second exhaust gas outlet duct capable of evacuating exhaust gases from the pressure wave compressor.

The invention advantageously takes advantage of the pressure wave compressor (PWS) to allow introduction into the combustion chamber compressed gas mixtures whose compositions are independently controlled by the two exhaust gas outlet ducts.

The invention makes it possible to obtain different recycled exhaust gas rates in the first and second admixtures admitted into the combustion chamber and thus allows stratification of the fluids in the combustion chamber of the engine.

For this purpose, the exhaust gas outlet pipes may have different sections so as to independently adjust the recycled exhaust gas rates in the first and second mixtures.

Alternatively, the engine may comprise means for controlling a section of one of the exhaust gas outlet ducts so as to independently adjust recycled exhaust rates in the first and second mixtures.

• le système comprend des premiers moyens pour contrôler une section du premier conduit de sortie de gaz d'échappement et des deuxièmes moyens pour contrôler une section du deuxième conduit de sortie de gaz d'échappement,
• les moyens pour contrôler une section de l'un des conduits de sortie de gaz d'échappement comprennent une portion de conduit présentant un étranglement,
• les moyens pour contrôler une section de l'un des conduits de sortie de gaz d'échappement comprennent une vanne apte à être commandée pour modifier la section dudit conduit,
• le système comprend une unité de commande programmée pour commander la vanne en fonction du régime moteur

The invention may advantageously have the following characteristics:

• the system comprises first means for controlling a section of the first exhaust gas outlet duct and second means for controlling a section of the second exhaust gas outlet duct,
• the means for controlling a section of one of the exhaust gas outlet ducts comprises a portion of duct having a throttling,
• the means for controlling a section of one of the exhaust gas outlet pipes comprises a valve which can be controlled to modify the section of said duct,
• the system includes a control unit programmed to control the valve according to the engine speed

• amener un premier mélange contenant de l'air et des gaz d'échappement recyclés par un premier conduit d'alimentation depuis un compresseur à onde de pression vers une chambre d'admission du moteur,
• évacuer des gaz d'échappement par un premier conduit de sortie de gaz d'échappement depuis le compresseur à onde de pression,

caractérisé en ce qu'il comprend en outre des étapes consistant à :

• amener un deuxième mélange contenant de l'air et des gaz d'échappement recyclés par un deuxième conduit d'alimentation depuis le compresseur à onde de pression vers la chambre d'admission du moteur,
• évacuer des gaz d'échappement par un deuxième conduit de sortie de gaz d'échappement depuis le compresseur à onde de pression.

The invention also relates to a method of supplying an engine, comprising the steps of:

• supplying a first mixture containing air and recycled exhaust gas through a first supply line from a pressure wave compressor to an engine inlet chamber,
• evacuating exhaust gases through a first exhaust gas outlet duct from the pressure wave compressor,

characterized by further comprising steps of:

• supplying a second mixture containing recycled air and exhaust gas through a second supply conduit from the pressure wave compressor to the engine inlet chamber,
• evacuating exhaust gases through a second exhaust gas outlet duct from the pressure wave compressor.

The method may include a step of controlling a section of one of the exhaust gas outlet conduits to independently regulate recycled exhaust rates in the first and second mixtures.

The method may comprise a step of independently controlling a section of the first exhaust gas outlet duct and a section of the second exhaust gas outlet duct.

According to this method, a section of one of the exhaust gas outlet ducts can be controlled by means of a channel portion having a throttling.

The method may include a step of controlling a valve to modify a section of an exhaust gas outlet conduit.

The valve can be controlled by a control unit programmed for this purpose, depending on the engine speed.

• la figure 1 représente de manière schématique un moteur équipé d'un système d'alimentation d'un moteur conforme à un mode de réalisation de l'invention,
• la figure 2 représente de manière schématique deux parties d'un stator de compresseur à onde de pression, l'une des parties étant destinée à être connectée à un circuit d'échappement et l'autre partie est destinée à être connectée à un circuit d'admission,
• les figures 3 à 6 représentent de manière schématique différentes étapes d'un procédé d'alimentation d'un moteur conforme à l'invention.

Other features and advantages will become apparent from the description which follows, which is purely illustrative and nonlimiting and should be read with reference to the appended figures among which:

• FIG. 1 schematically represents an engine equipped with a power supply system for an engine according to one embodiment of the invention,
• FIG. 2 schematically shows two parts of a pressure wave compressor stator, one of the parts being intended to be connected to an exhaust circuit and the other part to being connected to a circuit of 'admission,
• Figures 3 to 6 show schematically different steps of a power supply method of an engine according to the invention.

Figure 1 schematically shows a motor 1 and a motor supply system 1.

The supply system comprises a compressor with a pressure wave 2, an intake circuit 3 able to bring fresh air into a combustion chamber of the engine 1 and an exhaust system 4 able to evacuate gases from the engine. exhaust produced by combustion of fuel in the combustion chamber of the engine 1.

• un conduit 31 d'entrée d'air frais apte à amener de l'air frais en provenance de l'extérieur du véhicule vers le compresseur à onde de pression 2,
• un premier conduit 32 d'alimentation apte à amener un premier mélange contenant de l'air et des gaz d'échappement recyclés depuis le compresseur à onde de pression 2 vers la chambre de combustion du moteur 1, et
• un deuxième conduit 33 d'alimentation apte à amener un deuxième mélange contenant de l'air et des gaz d'échappement recyclés depuis le compresseur à onde de pression 2 vers la chambre de combustion du moteur 1.

The intake circuit 3 comprises:

• a fresh air inlet duct 31 capable of supplying fresh air from outside the vehicle to the pressure wave compressor 2,
• a first supply duct 32 capable of supplying a first mixture containing air and recycled exhaust gases from the pressure wave compressor 2 to the combustion chamber of the engine 1, and
• a second supply duct 33 capable of supplying a second mixture containing air and recycled exhaust gases from the pressure wave compressor 2 to the combustion chamber of the engine 1.

The supply ducts 32 and 33 make it possible to bring into the chamber a first mixture and a second mixture having different recycled exhaust gas contents so as to create stratification in the combustion chamber.

• un conduit 41 d'entrée de gaz d'échappement apte à amener des gaz d'échappement en provenance du moteur 1 vers le compresseur à onde de pression 2,
• un premier conduit 42 de sortie de gaz d'échappement apte à évacuer des gaz d'échappement depuis le compresseur à onde de pression 2, et
• un deuxième conduit 43 de sortie de gaz d'échappement également apte à évacuer des gaz d'échappement depuis le compresseur à onde de pression 2.

The exhaust circuit 4 comprises:

• an exhaust gas inlet duct 41 capable of supplying exhaust gases from the engine 1 to the pressure wave compressor 2,
• a first exhaust gas outlet pipe 42 capable of evacuating exhaust gases from the pressure wave compressor 2, and
• a second exhaust gas outlet pipe 43 which is also capable of evacuating exhaust gases from the pressure wave compressor 2.

Furthermore, the feed system comprises means for controlling the sections of the exhaust gas outlet ducts. For this purpose, the first conduit 42 and the second conduit 43 are respectively provided with butterfly valves 44 and 45. The butterfly valves are able to be controlled by an electronic control unit 5 (ECU) of the vehicle.

The pressure wave compressor 2 conventionally comprises a rotor driven in rotation by the motor 1 and a stator. The rotor comprises one or more channels extending in radial directions thereof.

Figure 2 schematically shows two parts 23 and 24 of the stator of the pressure wave compressor.

The intake portion 23 of the stator comprises openings for communicating a channel of the rotor with the intake circuit 3.

More specifically, the intake portion 23 comprises two openings 230 and 231 low pressure and two openings 232 and 233 high pressure. The openings 230 and 231 low pressure are connected to the duct 31 fresh air inlet. The openings 232 and 233 high pressure are respectively connected to the supply ducts 32 and 33.

The exhaust portion 24 of the stator comprises openings for communicating the rotor channel with the exhaust circuit 4.

Specifically, the exhaust portion 24 comprises two openings 240 and 241 low pressure and two openings 242 and 243 high pressure. The low pressure openings 240 and 241 are connected to the exhaust gas inlet duct 41. The openings 242 and 243 high pressure are respectively connected to the exhaust gas outlet pipes 42 and 43 respectively.

• le conduit 41 d'entrée de gaz d'échappement et le premier conduit 32 d'alimentation, par l'intermédiaire des ouvertures 232 et 241,
• le conduit 31 d'entrée d'air frais et le premier conduit 42 de sortie de gaz d'échappement, par l'intermédiaire des ouvertures 231 et 242,
• le conduit 41 d'entrée de gaz d'échappement et le deuxième conduit 33 d'alimentation, par l'intermédiaire des ouvertures 233 et 240,
• le conduit 31 d'entrée d'air frais et le deuxième conduit 43 de sortie de gaz d'échappement, par l'intermédiaire des ouvertures 230 et 243.

During a rotation of the rotor (according to the arrow), the rotor channel successively communicates:

• the exhaust gas inlet duct 41 and the first supply duct 32, through the openings 232 and 241,
• the fresh air intake duct 31 and the first exhaust gas outlet duct 42, through the openings 231 and 242,
• the exhaust gas inlet duct 41 and the second supply duct 33, via the openings 233 and 240,
• the fresh air intake duct 31 and the second exhaust gas outlet duct 43, through the openings 230 and 243.

Figures 3 to 6 show schematically the various steps of the motor supply method.

In a first step (FIG. 3), the exhaust gas inlet duct 41 is put in communication with the first supply duct 32 via the channel 20. The exhaust gases coming from the duct 41 enter in the channel 20, which causes a shock wave which has the effect of expelling a first mixture comprising air and exhaust gas to the first conduit 32 supply.

In a second step (FIG. 4), the fresh air intake duct 31 is put into communication with the first exhaust gas outlet duct 42. The air-exhaust mixture contained in the channel 20 is discharged from the channel 20 by the first exhaust gas outlet pipe 42. Fresh air is introduced into the channel 20 via the fresh air intake duct 31.

In a third step (FIG. 5), the exhaust gas inlet duct 41 is placed in communication with the second supply duct 33. The exhaust gas from the conduit 41 enters the channel 20, which causes a shock wave which has the effect of expelling a second mixture comprising air and exhaust gas to the second conduit 33 of food.

According to a fourth step (FIG. 6), the fresh air intake duct 31 is put into communication with the second exhaust gas outlet duct 43. The air-exhaust gas mixture contained in the channel 20 is discharged from the channel 20 by the second exhaust gas outlet pipe 43. Fresh air is introduced into the channel 20 via the fresh air intake duct 31.

The electronic control unit 5 (ECU) is programmed to control the opening of the valves 44 and 45 so as to respectively adjust the sections of the first conduit 42 and the second conduit 43 of exhaust gas outlet able to evacuate gases exhaust.

Adjusting the opening of the valve 44 makes it possible to adjust the expulsion of the gases contained in the channel 20 during the second step.

Therefore, adjusting the opening of the valve 44 makes it possible to adjust the rate of exhaust gas contained in the channel 20 during the third step that follows.

Similarly, adjusting the opening of the valve 45 makes it possible to adjust the expulsion of the gases contained in the channel 20 during the fourth step.

Therefore, adjusting the opening of the valve 45 makes it possible to adjust the rate of exhaust gas contained in the channel 20 during the first step that follows.

Thus, the valves 44 and 45 independently control the recycled exhaust gas rates injected into the combustion chamber of the engine by the first intake channel 32 and the second intake channel 33. It is thus possible to adjust the valves 44 and 45 to obtain different recycled exhaust gas rates in the channels 32 and 33 so as to form in the combustion chamber a stratification of gases.

The valves 44 and 45 are controlled by the electronic control unit 5 (ECU) of the vehicle which controls the operation of the engine 1. The electronic control unit 5 is programmed to independently control the opening of the valves 44 and 45 according to the engine speed to obtain a suitable stratification in the combustion chamber of the engine.

• Q ₃₂, le débit dans le premier conduit 32 d'alimentation,
• Q ₃₃, le débit dans le deuxième conduit 33 d'alimentation,
• T ₃₂, la température dans le premier conduit 32 d'alimentation,
• T ₃₃, la température dans le deuxième conduit 33 d'alimentation,
• T ₃₁, la température dans le conduit 31 d'entrée d'air frais,
• T ₄₁, la température dans le conduit 41 d'entrée de gaz d'échappement,
• Q _Carburant , le débit de carburant injecté dans le moteur 1,
• [O ₂], la concentration en dioxygène dans le conduit 41 d'entrée de gaz d'échappement.

The power system may include sensors for measuring the following parameters:

• Q ₃₂ , the flow rate in the first supply duct 32,
• Q ₃₃ , the flow rate in the second supply conduit 33,
• T ₃₂ , the temperature in the first supply duct 32,
• T ₃₃ , the temperature in the second supply conduit 33,
• T ₃₁ , the temperature in the duct 31 for fresh air inlet,
• T ₄₁ , the temperature in the duct 41 of the exhaust gas inlet,
• Q _Fuel , the flow of fuel injected into the engine 1,
• [ O ₂ ] , the dioxygen concentration in the conduit 41 of the exhaust gas inlet.

$$\frac{Q_{\mathrm{Air}}}{Q_{\mathrm{Carburant}}}=\frac{14,5\times 0,233}{0,233-\left[O_2\right]}$$

$$Q_{32}+Q_{33}=Q_{\mathrm{Air}}+Q_{\mathrm{EGR}}$$

$$Q_{\mathrm{EGR}}=Q_{32}\times x_{32}+Q_{33}\times x_{33}$$

où
χ ₃₂ est le taux de gaz d'échappement recyclés contenus dans le conduit 32,
χ ₃₃ est le taux de gaz d'échappement recyclés contenus dans le conduit 33,
Q _Air est le débit d'air admis dans le moteur,
Q _EGR est le débit de gaz d'échappement recyclés admis dans le moteur,
Q₄₁ est le débit dans le conduit 41 d'entrée de gaz d'échappement.We have the following relationships: $$x_{32}-x_{33}=\frac{T_{32}-T_{33}}{T_{31}-T_{41}}$$

$$\frac{Q_{\mathrm{Air}}}{Q_{\mathrm{Fuel}}}=\frac{14,5\times 0,233}{0,233-\left[O_{\mathrm{two}}\right]}$$

$${\mathrm{<figure-callout\; id="32"\; label="Q"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{32}<figure-callout\; id="33"\; label="+\; Q"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">+\; </figure-callout>Q_{}{}_{33}=Q_{\mathrm{Air}}+Q_{\mathrm{EGR}}$$

$$Q_{\mathrm{EGR}}={\mathrm{<figure-callout\; id="32"\; label="Q"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{32}\times x_{32}+{\mathrm{<figure-callout\; id="33"\; label="Q"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{33}\times x_{33}$$

or
χ ₃₂ is the recycled exhaust gas content contained in the duct 32,
χ ₃₃ is the rate of recycled exhaust gas contained in the conduit 33,
Q _Air is the air flow admitted into the engine,
Q _EGR is the flow of recycled exhaust gases admitted into the engine,
Q ₄₁ is the flow rate in the exhaust gas inlet duct 41.

$$x_{33}=\frac{Q_{\mathrm{EGR}}+Q_{32}\times \frac{T_{32}-T_{33}}{T_{31}-T_{41}}}{Q_{32}+Q_{33}}$$

The electronic control unit 5 is able to estimate the rates χ ₃₂ and χ ₃₃ of recycled exhaust gas contained in the conduits 32 and 33 supply, from the measurements provided by the sensors. $$x_{32}=\frac{Q_{\mathrm{EGR}}+{\mathrm{<figure-callout\; id="33"\; label="Q"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{33}\times \frac{T_{32}-T_{33}}{T_{31}-T_{41}}}{{\mathrm{<figure-callout\; id="32"\; label="Q"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{32}+Q_{33}}$$

$$x_{33}=\frac{Q_{\mathrm{EGR}}+{\mathrm{<figure-callout\; id="32"\; label="Q"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{32}\times \frac{T_{32}-T_{33}}{T_{31}-T_{41}}}{{\mathrm{<figure-callout\; id="32"\; label="Q"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{32}<figure-callout\; id="33"\; label="+\; Q"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">+\; </figure-callout>Q_{}{}_{33}}$$

The electronic control unit 5 is able to adjust the opening of the valves 44 and 45 to precisely adjust the rates χ ₃₂ and χ ₃₃ of recycled exhaust gas according to the engine speed.

An embodiment has been described in which the means for controlling the sections of the exhaust gas outlet pipes 42 and 43 comprise valves 44 and 45. However, as will be understood, other means may be envisaged. .

In particular, the means for controlling the sections of the exhaust gas outlet pipes 42 and 43 may comprise a portion of duct having a narrowed or constricted section. Such throttling makes it possible to permanently adjust the quantity of gas expelled by the exhaust gas outlet duct.

Claims (12)

Motor (1) comprising: a first feed duct (32) adapted to supply a first mixture containing air and recycled exhaust gases from a pressure wave compressor (2) to a combustion chamber of the engine (1), a first exhaust gas outlet duct (42) adapted to evacuate exhaust gases from the pressure wave compressor (2), characterized in that it further comprises
a second supply duct (33) capable of supplying a second mixture containing air and recycled exhaust gases from the pressure wave compressor (2) to the combustion chamber of the engine (1), and
a second exhaust gas outlet conduit (43) adapted to exhaust exhaust gases from the pressure wave compressor (2). An engine according to claim 1, wherein the exhaust gas outlet pipes (42, 43) have different cross-sections so as to independently regulate the exhaust gas rates (χ ₃₂ , χ ₃₃ ) recycled in the exhaust pipes. first and second mixtures. An engine according to claim 1, further comprising means (44, 45) for controlling a section of one of the exhaust gas outlet conduits (42, 43) to independently adjust rates (χ ₃₂ , χ ₃₃ ) of recycled exhaust gas in the first and second mixtures. An engine according to claim 3, comprising first means (44) for controlling a section of the first exhaust gas outlet conduit (42) and second means (45) for controlling a section of the second exhaust gas outlet conduit (43). exhaust gas. Engine according to one of claims 3 or 4, wherein the means for controlling a section of one of the exhaust gas outlet conduits (42, 43) comprises a portion of duct having a throttling. Engine according to one of claims 3 or 4, wherein the means for controlling a section of one of the exhaust gas outlet pipes (42, 43) comprises a valve (44, 45) controllable for modify the section of said conduit. A method of supplying an engine, comprising the steps of: supplying a first mixture containing air and recycled exhaust gas through a first supply line (32) from a pressure wave compressor (2) to an engine inlet chamber (1), evacuating exhaust gases through a first exhaust gas outlet pipe (42) from the pressure wave compressor (2), characterized by further comprising steps of: supplying a second mixture containing recycled air and exhaust gas through a second supply conduit (33) from the pressure wave compressor (2) to the engine inlet chamber (1), discharging exhaust gas through a second exhaust gas outlet pipe (43) from the pressure wave compressor (2). The method of claim 7, further comprising a step of controlling a section of one of the exhaust gas outlet conduits (42, 43) to independently control rates (x ₃₂ , x ₃₃ ) exhaust gas recycled in the first and second mixtures. The method of claim 8 including a step of independently controlling a section of the first exhaust gas outlet conduit (42) and a section of the second exhaust gas outlet conduit (43). Method according to one of claims 8 or 9, wherein a section of one of the exhaust gas outlet conduits (42, 43) is controlled by means of a channel portion having a throttling. The method of one of claims 8 or 9, comprising a step of controlling a valve (44,45) to modify a section of an exhaust gas outlet conduit (42,43). The method of claim 11, wherein the valve (44, 45) is controlled by a control unit (5) according to the engine speed.

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