Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B17/00—Engines characterised by means for effecting stratification of charge in cylinders
  • F02B17/005—Engines characterised by means for effecting stratification of charge in cylinders having direct injection in the combustion chamber
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B19/00—Engines characterised by precombustion chambers
  • F02B19/12—Engines characterised by precombustion chambers with positive ignition
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/10—Internal combustion engine [ICE] based vehicles
  • Y02T10/12—Improving ICE efficiencies

Definitions

• the present invention relates to an internal combustion engine with supercharging and pre-chamber spark plug, an ignition method and an application of the method to the engine. It is intended for the gasoline, gas or other internal combustion engine industry in two or four times, as well for motorized vehicles such as motorcycles, cars, aircraft ... as motorized devices such as generators, tools or others. Although preferably implemented in a piston and crankshaft engine, it can be applied to an engine of the rotary type.
• Each drive member comprises a combustion chamber, also called a cylinder, of a combustible mixture of the type of fuel and oxidizing components, generally petrol and air, and provided with a compression system, in this case a piston for this type. engine, a fuel mixture ignition system by an electric spark generator as well as sequential flow devices for fuel and oxidizing components and for combustion products.
• This type of engine is conventionally known and will not be detailed here.
• a booster is generally a turbine actuated by the exhaust gases and which compresses the air which must be admitted into the cylinders.
• Other types of blowers can be used, turbo-compressors, simple compressors, pressure wave systems, etc.
• Supercharged engines require thermal protection of the booster system. Indeed, considering the case of a turbine actuated by the exhaust gases, it is exposed directly to the flow of hot gases leaving the engine while the turbine has a maximum allowable, destructive, limited temperature. Usually, to overcome this drawback, enrichment is used by adding fuel to limit the temperature of the burnt gases leaving the engine. In fact, the excess fuel thus supplied cannot burn because the quantity of air present in the cylinder is insufficient (the quantity of air present in the cylinder only burns fuel equivalent to the richness 1), and this excess fuel by vaporizing (latent heat of vaporization) allows the charge to cool. The gases therefore leave the cylinder less hot.
• EP-0957246 discloses a gas engine (CH 4 ) whose ignition control is achieved by injecting a small amount of liquid fuel into a prechamber.
• the object of the invention is to propose an ignition system making it possible to reduce the enrichment in a supercharged engine while allowing correct combustion, that is to say with a correct combustion efficiency, even in the case of preparation. unfavorable mixture.
• the ignition system comes in place of the spark plug on a conventional engine and no specific arrangement of the cylinder head is necessary.
• the ignition system comprises in its part in relation to the combustion chamber, a substantially spherical head pierced with holes or orifices of passage or passages, these terms being equivalent. Inside this head, there are one or more electrodes making it possible to create a spark by applying a voltage between them.
• the invention relates to an internal combustion engine with at least one drive member, the drive member comprising:
• the ignition system comprises a closed substantially spherical head with a wall enclosing the igniter in a prechamber, the head comprising a set of orifices intended to make the combustion chamber and the prechamber communicate so that the mixture fuel can pass into the prechamber.
• the igniter includes an electric spark generator
• the ignition system is a pre-chamber candle
• the ignition system includes a system for introducing fuel and oxidizing components directly into the prechamber
• the ignition system includes an introduction device allowing the direct introduction of a combustible mixture into the prechamber, the partition wall between the prechamber and the combustion chamber of the head is convex towards the outside of the prechamber,
• the partition wall between the prechamber and the combustion chamber of the head is concave towards the outside of the prechamber
• the partition wall between the prechamber and the combustion chamber of the head is substantially a polyhedron, a cone, - the spark plug head has a wall of the grid or porous material type,
• the partition wall between the prechamber and the combustion chamber of the head is made of a material with thermal conductivity greater than 10W / K / m
• the partition wall between the prechamber and the combustion chamber of the head is made in a material with thermal conductivity preferably greater than 30W / K / m
• the partition wall between the prechamber and the combustion chamber of the head is made of copper alloy with high conductivity
• the copper alloy is CuCrI Zr
• the partition wall between the prechamber and the combustion chamber of the head comprises a refractory material
• the wall of the head is covered with a substance facilitating the reactive combination of the fuel and oxidizing components and / or the ultimate degradation of the products combustion
• each orifice of the prechamber on the head has a diameter less than or equal to 3 mm
• the orifices of the prechamber of the head are organized on the head so that the combustion of the combustible mixture in the prechamber causes jets of material through the orifices towards the combustion chamber distributed so as to ensure homogeneity of combustion of the fuel mixture substantially throughout the combustion chamber, - at least one of the passage devices is a direct injector in the chamber combustion for all or part of the fuel and / or oxidizing components,
• the compression system is a piston in a cylindrical combustion chamber with a central axis, the injector being disposed substantially axially opposite the piston and the ignition system laterally with respect to the injector, and the orifices are mainly arranged towards the axis,
• - compression system is a piston in a cylindrical combustion chamber with a central axis, the ignition system being disposed substantially axially opposite the piston and the injector laterally with respect to the spark plug, and the orifices are distributed regularly over the surface of the head,
• the compression system is a piston in a cylindrical combustion chamber with a central axis, the injector and the ignition system being arranged laterally with respect to said axis, and the orifices are mainly arranged towards the axis,
• the head of the spark plug is arranged on a part of the path of the fuel components injected so that said head can be wetted by said fuel components during their direct injection
• each orifice allowing the passage of the flame front has a diameter of between 1 and 3 mm
• the orifices with passage dimensions not allowing the passage of a flame front from the prechamber to the combustion chamber while allowing the passage of unstable species resulting from the combustion in the prechamber to allow self-ignition of the combustible mixture in the combustion chamber,
• the head can therefore have orifices of the two preceding types, that is to say leaving and not letting the flame front pass),
• the number of orifices allowing the propagation of a flame front formed in the head of the prechamber body varies from 1 to 5 and preferably is 1 and the number of orifices not allowing the propagation of a front of flame varies from 1 to 20, preferably from 3 to 15,
• each orifice which does not allow the flame front to pass has a diameter of less than 1 mm
• each orifice which does not allow the flame front to pass has a diameter of between 0.5 and 1 mm, - each orifice has a length less than its diameter
• the engine also comprises means making it possible to re-inject with the oxidizing components part of the combustion products,
• the injector is with multiple jets, one of the jets being directed towards the head,
• the richness of the mixture is greater than or equal to one in at least one operating mode of the engine.
• the invention also relates to a method of igniting an internal combustion engine having at least one engine member, the engine member comprising:
• a combustion chamber of a combustible mixture of the type of fuel and oxidizing components provided with a compression system, - a fuel mixture ignition system by an igniter,
• an ignition system comprising a closed substantially spherical head with a wall enclosing the igniter in a prechamber, the head comprising a set of orifices intended to make the combustion chamber and the prechamber communicate so that the mixture fuel can pass into the prechamber,
• An ignition of the combustible mixture in the prechamber is caused by the igniter, the orifices of the prechamber allowing the ignition of the combustible mixture in the combustion chamber.
• the preceding steps are also implemented in a process characterized in that unstable species resulting from combustion in the prechamber are allowed to pass through the orifices in order to allow self-ignition of the combustible mixture of the combustion chamber without however leaving pass the flame front from the prechamber to the combustion chamber.
• the invention also relates to an application of the methods according to the preceding characteristics to the engine according to one or more of the characteristics of the motors listed above, and in particular, direct injection is implemented.
• the invention finally relates to a pre-chamber candle for implementation in the engine of the invention and according to one or more of the corresponding characteristics previously listed.
• the implementation of the invention in a supercharged engine therefore makes it possible to limit the enrichment at high load because the combustion is faster and ends earlier in the engine cycle.
• the gases from the combustion therefore leave the cylinder less hot because the time between the end of combustion and the valve opening is longer.
• the enrichment required to protect the turbine can therefore be less, hence lower consumption on this type of supercharged engine compared to a conventional spark plug ignition.
• the other advantages provided by the present invention are the protection of the spark plug electrodes. The probability of the presence of a fuel mixture in the vicinity of the electrodes is higher.
• the Prechamber ignition system allows for more stable combustion, even in the case of an inconsistent mixture. Indeed, on the one hand several flame fronts reach different zones of the combustion chamber and on the other hand, the radicals emitted by the orifices of the igniter seed the combustion chamber at different points and under the combined effects of the pressure and temperature generated by the rise of the piston, these precursors ignite the mixture at different points in the combustion chamber. The probability of having precursors in a zone favorable to the initiation of combustion is therefore much higher than in the case of a conventional candle.
• the wall of the prechamber protects the electrodes from the impact of liquid fuel on them, resulting in better behavior when starting cold and reducing fouling of the spark plug.
• FIG. 1 which represents seen in the prechamber the progression of the combustion produced by a spark
• FIG. 2 which represents seen from the combustion chamber the various orifices of the spark plug head
• Figures 3, 4, 5, 6 which represent a sectional view of a cylinder for different operating phases of an engine according to the invention in the case of direct injection
• Figure 7 which shows an exemplary embodiment of a spark plug type ignition system partially in section
• Figure 8 which shows an exemplary embodiment of a head of the ignition system.
• Ignition systems the igniter of which is a spark gap intended to produce electric sparks, of the spark plug type, may have different configurations depending on the type of engine and / or the desired performances.
• the candles can be longer or shorter.
• the invention which implements a pre-chamber candle can employ different configurations of candles and will give a particular example at the end of the description.
• the candle comprises a prechamber according to characteristics which will now be specified.
• the S / V ratio As for the S / V ratio, it is a quality indicator. The lower this ratio, the better the efficiency of use of the oxidant and fuel. The optimal case is that of the spherical prechamber.
• the ignition system of the pre-chamber spark plug type of the invention is a component which does not require any particular machining at the level of the engine.
• the implantation can be done in a conventional spark plug well since its diameter can be less than or equal to 14 mm.
• the volume of the prechamber can be between 0.2 and 2 cm 3 .
• the prechamber has a volume of less than 1.5 cm 3 , generally between 0.5 cm 3 and 1.5 cm 3 .
• the ratio between the volume of the prechamber and the dead volume of the main chamber varies between 0, 1 and 5%, preferably between 0, 1 and 2%.
• the shape of the head of the ignition system is preferably a spherical cap.
• the ignition system may also include an inlet allowing the prechamber to be supplied directly with a combustible mixture formed upstream or the introduction of fuel, the air then being mixed with the fuel in the prechamber.
• the ignition system comprises in its part in relation to the combustion chamber, a spherical head pierced with holes or orifices or passages, these terms being equivalent in the context of the invention. Inside this head, there is the igniter in the form of one or more electrodes making it possible to create a spark by applying a voltage between them.
• the CuCr-iZr alloy is a grade of the CRM 16x alloy with a nominal composition Cr> 0.4%, Zr from 0.022% to 0.1% and the rest of the copper.
• the prechamber can be made of a material having a thermal conductivity greater than 10W / K / m and preferably greater than 30W / K / m.
• a material having a thermal conductivity greater than 10W / K / m and preferably greater than 30W / K / m.
• the use of such a material, preferably a copper alloy allows energy to be evacuated at the level of the prechamber wall and thus to mitigate the appearance of hot spots at the prechamber.
• the CuCrI Zr alloy the thermal conductivity at 20 ° C of 320W / K / m.
• the following table presents various binary brasses, cupro-nickels, cupro-aluminum and nickel silver which can be used as material for the prechamber body.
• the level of thermal conductivity as well as the behavior mechanical at high temperature (450-1000K) conditions the choice of material.
• Cupro-aluminum 75 to 84 W / (m • K) (Cu Al 5, Cu Al 6), 38 to 46 W / (m • K) (Cu Al 10 Fe 5 Ni 5)
• This type of pre-chamber spark plug is preferably used with an engine having an optimized cylinder head permeability to the detriment of the aerodynamics of the combustion chamber. Indeed, the combustion mode resulting from the use of the pre-chamber candle allows a combustion speed sufficient to dispense with an increase in the combustion speed via the aerodynamics of the combustion chamber.
• the invention can be implemented both on a conventional supercharged engine in which a combustible mixture is introduced into the combustion chamber, that is to say that the mixture was made upstream of the engine member, as on an engine with direct injection of fuel components.
• FIG. 1 therefore represents, seen in the prechamber 1, the progression of combustion 2 produced by a spark 3.
• FIG. 2 therefore represents, seen from the combustion chamber 4, the various orifices 5 in the wall of the spark plug head 6 allowing communications between the prechamber 1 and the combustion chamber 4, also called the main chamber. Thanks to these communications, on the one hand, of the combustible mixture passes from the combustion chamber to the prechamber and, on the other hand, after ignition in the prechamber, the combustible mixture of the combustion chamber may be caused to ignite.
• the arrangement of the orifices allows a substantially homogeneous distribution of the flame front and / or of the unstable species which allow the ignition of the combustible mixture of the combustion chamber.
• the candle and its head are a single component which replaces a traditional candle which does not require modification of the cylinder head passage for the candle.
• the ignition system thus consists of a device which takes the place of the traditional candle.
• the system generating the spark be modified according to the shape of the head and, for example that the central electrode advances further into the head and approaches the wall thereof so that the an electric arc is formed between the central electrode and the wall of the head.
• the wall must include an electrically conductive material for the return to ground of the spark current.
• the spark plug head is a removable part, for example by screwing, and that it can be unscrewed to access / to the spark plug electrodes for a possible spacing adjustment or inspection.
• the head may be desirable for the head to extend laterally backwards in a screwing zone on the cylinder head so that it is maintained and does not risk unscrewing and falling into the combustion chamber following the motor trepidation.
• the examples given are purely indicative and that the invention can be declined according to various possibilities. We have thus seen that it was possible to use a head with orifices of both types, that is to say leaving and not letting the flame front pass. Similarly, the orientations of the orifices can be optimized depending on the relative arrangement of the various components in the engine.
• direct injection engines are generally penalized in preparation for the mixture compared to injection engines in intake ducts by problems of homogeneity of the mixture in the combustion chamber.
• direct injection engines present, in certain configuration configurations of the injector injector and of the spark plug, problems of direct impact of the fuel on the spark plug electrodes, hence problems of cold starting. and fouling of the spark plug electrodes.
• direct injection engines are sensitive to the impact of relatively cold fuel on the cylinder walls. However, to ensure correct initiation (ignition), it may be necessary to have a jet large enough so that it passes near the spark plug, which implies a significant wall effect.
• FIG. 3 the phase of injection of the fuel components by the injector 8 is in progress and a part of the fuels comes to wet the head 6 of the spark plug 7 which envelops the prechamber.
• FIG. 3 the phase of injection of the fuel components by the injector 8 is in progress and a part of the fuels comes to wet the head 6 of the spark plug 7 which envelops the prechamber.
• the engine being hot, the fuels are vaporized both on the piston 9 which has a “piston bowl” and on the head 6 of the spark plug 7.
• the phase of compression is started and the combustible mixture passes from the combustion chamber 4 to the prechamber 1 of the spark plug 7.
• the combustion phase is started from the prechamber 1 in which a spark has been produced and by passage , through the orifices 5 of the head 6, of the flame front and / or according to the type of orifice, unstable species for propagation towards the combustion chamber 4.
• the implementation of the invention allows a reduction in knocking, this being in particular perceptible in the case of the operation of the motor at high load.
• low engine load operation is meant the engine operating range from idle to a quarter of the full engine load, preferably the range from idle to 10% of full load in the case of an atmospheric engine and the range from idle to 5% of full load in the case of a highly supercharged engine.
• holes are implemented in the wall of the head which have a differential effect of passage or not of the flame front as a function of the engine load.
• This effect can be obtained for example by at least one orifice allowing the propagation of a flame front at low load and at least one orifice not allowing the propagation of a flame front under all load conditions or, then, by only at least one orifice allowing the propagation of a flame front at low charge.
• the flame front can pass from the prechamber towards the main combustion chamber by means of the passage (s) allowing the propagation of a flame front and the ignition is thus caused of the main fuel mixture by means of a flame front.
• the structure of the orifices which let the flame front pass at low charge is such that, at high charge, the flame front no longer passes, said orifices causing extinction of the flame front and these are then the unstable compounds resulting from the combustion of the combustible mixture of the prechamber which lead to self-ignition in mass of the main combustible mixture sown with unstable compounds in the main chamber.
• the pressure differential between the prechamber and the main chamber prevents the flame front from propagating from the prechamber to the main chamber.
• the passages allow the flow of unstable compounds to pass from the prechamber to the main chamber and, when the piston rises, the compression produces mass self-ignition of the main mixture.
• the internal and / or external faces of the wall of the head of the prechamber as well as, optionally, the walls of the orifices are coated with '' a refractory coating, such as, for example, coatings of Al 2 O 3 , ZrY (not necessarily stoichiometric) and TiB 2 .
• the thickness of these coatings is generally between 5 and 100 ⁇ m, preferably 1 to 50 ⁇ m. This increases the combustion efficiency in the prechamber and improves operation at low loads, in particular in the case of highly supercharged engines.
• FIG. 7 a particular example of a pre-chamber candle which includes a body in extension of the head.
• the spark plug 7 is mounted screwed into a thread 10a of the cylinder head 10 closing a cylinder of an internal combustion engine of which only a part has been shown.
• the candle 7 comprises a body 12 of prechamber 1 of generally tubular shape and comprising a head 12a of generally convex shape, preferably having the shape of a spherical cap.
• the head 12a of the body 12 of prechamber 1 constitutes a partition wall between the combustion chamber 4 and the prechamber 1.
• the prechamber 1 comprises the igniter comprising a central electrode 13 and a ground electrode 14.
• the head 12a constituting the partition wall between the combustion chamber 4 and the prechamber 1 is provided of various passage orifices 5, shown in more detail in FIG. 8.
• the orifices 5, of generally cylindrical shape comprise a passage 5a, having a large diameter, that is to say a diameter greater than 1 mm, generally between more than 1 mm and 3 mm and a series orifices 5b to 5i (7 in the embodiment of FIG. 8) having a small diameter, that is to say less than or equal to 1 mm.
• the length of the passages is less than 1 mm and they are here oriented along radii of the hemispherical head 12a. It has also been seen that the orientation and / or the structure of the orifices can be adapted to the particular configuration of the elements of the engine.
• the head 12a can comprise several orifices of large diameter.
• the number and the size of the orifices must be such that no flame front can propagate from the prechamber to the combustion chamber when the engine is running at high load.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Combustion Methods Of Internal-Combustion Engines (AREA)
• Ignition Installations For Internal Combustion Engines (AREA)

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• 2002
  • 2002-10-18 FR FR0213016A patent/FR2846041B1/fr not_active Expired - Fee Related
• 2003
  • 2003-10-17 US US10/531,731 patent/US7243634B2/en not_active Expired - Fee Related
  • 2003-10-17 WO PCT/FR2003/003081 patent/WO2004036012A2/fr not_active Ceased
  • 2003-10-17 EP EP03778401A patent/EP1556591A2/de not_active Withdrawn
  • 2003-10-17 JP JP2004544400A patent/JP2006503216A/ja active Pending

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