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 direct injection 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.
• This type of engine includes one or more drive members.
• Each drive member includes a combustion chamber of a combustible mixture of fuel and oxidizer type, generally gasoline and air, and provided with a compression system, in this case a piston for this type of engine, a system ignition of the fuel mixture by an electric spark generator as well as sequential flow devices for fuel and oxidizing components and for combustion products.
• a compression system in this case a piston for this type of engine, a system ignition of the fuel mixture by an electric spark generator as well as sequential flow devices for fuel and oxidizing components and for combustion products.
• direct gasoline 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 configurations of the injector and spark plug arrangement, 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.
• patent EP-0831213 having for holder DAIMLERCHRYSLER AG, an internal combustion engine with direct injection is known which uses a spark ignition with a spark plug.
• An injector allows high pressure to directly inject fuel components into the combustion chamber.
• the spark plug simply has a sleeve which is open in the combustion chamber.
• EP-0957246 discloses a gaseous fuel (CH) combustion engine whose ignition control is achieved by injecting a small amount of liquid fuel into a prechamber.
• CH gaseous fuel
• the invention aims to provide an ignition system for correct combustion, that is to say with a correct combustion efficiency, even in cases of preparation of the unfavorable mixture.
• the ignition system comes in place of the conventional 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 passage orifices or passages, these terms being equivalent. Inside this head, there is an igniter, preferably 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 engine member, the engine member comprising: - a combustion chamber of a combustible mixture of the type of fuel and oxidizer components provided with a compression system,
• 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, and at least one of the passage devices is a direct injector into the combustion chamber for part or all of the fuel and / or oxidizing components.
• Direct injection can indeed relate to either fuels alone. Generally under high pressure of the order of 100 bars, or a fuel / oxidizer premix generally under low pressure of the order of 5 to 10 bars).
• the igniter is 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, - alternatively 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 candle 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 10 W / K / m
• the partition wall between the prechamber and the combustion chamber of the spark plug head is made of a material with thermal conductivity preferably greater than 30 W / 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 CuCrIZr
• the partition wall between the prechamber and the combustion chamber of the head comprises a refractory material
• the wall of the head of the spark plug is covered with a substance facilitating the reactive combination of the fuel and oxidizing components and / or the degradation ultimate combustion products
• the orifices of the prechamber on the head are cylindrical passages
• 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 at least three in number,
• 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 the combustion of the combustible mixture substantially in the whole of the combustion chamber,
• the compression system is a piston in a cylindrical combustion chamber with a central axis, the injector being arranged substantially axially opposite the piston and the system ignition 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 ignition system, and the orifices are distributed regularly on 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,
• - head 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, - at least one of the orifices with passage dimensions allowing the passage of a flame front from the prechamber to the combustion chamber,
• each orifice allowing the passage of the flame front has a diameter of between 1 and 3 mm, - at least one of 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 combustion in the prechamber in order to allow self-ignition of the combustible mixture of the combustion chamber,
• the head can therefore have orifices of the two previous 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 engine also comprises means making it possible to compress the oxidizing components upstream of the engine member in order to allow an over-supply,
• the injector is with multiple jets, one of the jets being directed towards the head, the jets are sequentially distributed over time,
• the fuel is exclusively liquid, in particular petrol.
• 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 oxidizer components provided with a compression system,
• 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,
• all the fuel and / or oxidizing components are introduced directly into the combustion chamber by one of the passage devices which is a direct injector, in addition, at least oxidizing components are introduced into said combustion chamber in order to form the combustible mixture,
• 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 motor according to one or more of the characteristics of the motors listed above.
• the invention finally relates to a prechamber plug for implementation in the engine of the invention and according to one or more of the corresponding characteristics previously listed.
• the prechamber ignition system makes it possible to obtain more stable combustion, even in the case of an inhomogeneous 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. in cold start and a reduction in the fouling of the spark plug. Then, it is possible to use an injector jet directly wetting the walls of the combustion prechamber, which has the effect of promoting the ascent of the fuel mixture inside the prechamber. This can have beneficial effects on start-up and initiation in general.
• the injection of fuel on the head of the hot igniter makes it possible to increase the robustness AI / AA by the effect of the vaporization of the fuel near the electrodes (Al corresponds to the advance to injection and AA in advance to ignition).
• Al corresponds to the advance to injection and AA in advance to 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 thus higher.
• the invention can also be implemented advantageously in the case of internal combustion engines with positive ignition and highly supercharged as will be seen later in detail.
• 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 according to different operating phases of the engine of the invention
• Figure 7 which represents an exemplary embodiment of a system of ignition type candle partially in section
• Figure 8 which shows an 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. for example the candles can be longer or shorter.
• the invention which implements a pre-chamber candle can employ different configurations of candles and a specific example will be given 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 the 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 enabling the prechamber to be supplied directly with a combustible mixture formed upstream or to introduce 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.
• 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.
• 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
• 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, the combustible mixture passes from the combustion chamber towards 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.
• FIG. 3 shows a drive member seen in axial section of a piston 9 and passing through an injector 8 and a spark plug 7.
• 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.
• Figure 4 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 compression phase is started and the combustible mixture passes from the combustion chamber 4 to the prechamber 1 of the spark plug 7.
• FIG. 3 shows a drive member seen in axial section of a piston 9 and passing through an injector 8 and a 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 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. It is also envisaged that 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. In the latter case, it 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. It will be understood that the examples given are purely indicative and that the invention can be declined according to various possibilities.
• Supercharged engines require thermal protection of the turbine. Indeed, it is exposed directly to the flow of hot gases leaving the engine while the turbine has a maximum allowable, destructive, limited temperature.
• enrichment is used by adding fuel to limit the temperature of the burnt gases leaving the engine.
• 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.
• this effect is proportional to the excess gasoline provided and this gasoline is only used to cool the gases, which leads to an increase in consumption.
• this knock-off effect is particularly noticeable in the case of the operation of the engine at high load.
• 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 load is such that, at high load, the flame front no longer passes, said orifices causing the extinction of the front flame and it is 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 inoculated with the 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.
• orifices leaving or not letting the flame front pass, whether under any load conditions or not, in order to obtain differential effects this time in volume, certain types of orifices being arranged on the head preferably to have combustion initiation effects in a more particular area of the combustion chamber.
• 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 coatings in AI2O3, ZrY (not necessarily stoichiometric) and TiB 2 .
• the thickness of these coatings is generally between 0.5 and 100 ⁇ m, preferably 1 to 50 ⁇ m.
• pre-chamber candles can be used.
• 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 with various passage orifices 5, shown more clearly detailed 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 of 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.
• the orientation and / or the structure of the orifices can be adapted to the particular configuration of the elements of the engine.
• a single orifice 5a of diameter greater than 1 mm has been shown (preferred embodiment)
• the head 12a can comprise several orifices of large diameter.
• the number and the size of the orifices must be such that no flame cannot 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 FR0213018A patent/FR2846043B1/fr not_active Expired - Fee Related
• 2003
  • 2003-10-17 EP EP03808762A patent/EP1556589A2/de not_active Withdrawn
  • 2003-10-17 JP JP2004544399A patent/JP2006503215A/ja active Pending
  • 2003-10-17 WO PCT/FR2003/003080 patent/WO2004036009A2/fr not_active Ceased
  • 2003-10-17 US US10/531,730 patent/US7237526B2/en not_active Expired - Fee Related

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