WO2009044225A1

WO2009044225A1 - A method of mixing in a combustion chamber of an internal combustion engine and a spark-ignition direct-injection stratified fuel-air charge internal combustion engine

Info

Publication number: WO2009044225A1
Application number: PCT/IB2007/004105
Authority: WO
Inventors: Volodymyr Anatoliyovych Korogodskyj; Igor Olegovych Kyrylyuk; Sergiy Georgiyovych Lomov
Original assignee: Kulygin, Viktor Ivanovych
Priority date: 2007-10-03
Filing date: 2007-12-27
Publication date: 2009-04-09
Also published as: UA87733C2

Abstract

The invention represents a method of mixing in a combustion chamber of a spark-ignition direct-injection stratified charge internal combustion engine a fuel-air mixture being ignited by a spark plug (5), the method comprising: the injection, in the compression stroke, of fuel to the combustion chamber charged with air,- fuel spraying onto the surface of the combustion chamber disposed in a cylinder head; the organization of air charge motion, wherein the fuel is injected and sprayed so that there is produced a cone-shaped fuel spray, which consists of a cone-shaped body of the spray cone and of a cone-shaped cavity within the body and which is directed so that a spark plug gap is inside the cavity and the motion of the air charge is directed uniformly from all sides along the combustion chamber surface towards the spark plug electrodes (6). Another aspect of invention is engine according to method of the invention.

Description

A METHOD OF MIXING IN A COMBUSTION CHAMBER OF AN INTERNAL COMBUSTION ENGINE AND A SPARK-IGNITION DIRECT- INJECTION STRATIFIED FUEL-AIR CHARGE INTERNAL COMBUSTION

ENGINE

The invention relates to mechanical engineering. More particularly, the invention relates to the field of propulsion engineering (spark-ignition direct-injection internal combustion engines (ICE)). The invention also relates to the organization of mixing and combustion processes, as well as to fuel-air charge stratification in an engine cylinder.

At present, due to the depletion of the worldwide reserves of organic fuel and a stable increase in its consumption level, especially as far as liquid fuel is concerned, the problem of its conservation and efficient use is becoming one of the most acute and of those requiring their immediate solutions. Internal combustion engines are the principal consumers of light liquid fuels, which produce over 80% of mechanical energy consumed by the mankind in its activity. Of these, spark-ignition internal combustion engines, both two-stroke and four-stroke ones, constitute a very great class in terms of the quantity of units produced worldwide. At the same time the content of harmful substances, contained in the exhaust gases of internal combustion engines, pollutes the atmosphere and causes the deterioration of the environment. Therefore, reduction in fuel consumption and harmful substance emissions with the exhaust gases is a topical issue.

The main fuel, which is used in internal combustion engines, is gasoline or diesel fuel produced by crude oil refining and consisting mostly of hydrocarbons (C_nH_m). As the fuel burns completely, heat is produced, and carbon dioxide (CO₂) and water vapor (H₂O) are produced. During the fuel combustion process, nitrogen oxides (NO_x) are produced as a result of the reactions of oxidation of nitrogen (N₂), contained in both fuel and atmospheric air, with oxygen (O₂) of the air. The amount of nitrogen oxides (NO_x) in the exhaust gases is determined mostly by combustion temperature, the level of nitrogen- and oxygen in combustion products.

Without giving special details, in a purely chemical aspect, the influence of harmful substances contained in the exhaust gases of an automobile on living organisms is reduced to the following: due to incomplete oxidation of a portion of gasoline hydrocarbons, carbon monoxides (CO) are produced which have a harmful effect on human health even at low concentration because of their more active, in comparison with oxygene, interaction with hemoglobin. Under high temperature conditions that develop in the engine cylinder, nitrogen is oxidized by oxygen of the air to nitrogen oxide (NO) and nitrogen dioxide (NO₂) which cause general weakness, vertigo and nausea. Sulfur (S) contained in gasoline is oxidized sulfur dioxide (SO₂) that disturbs breathing processes in humans and contributes to increase in atmospheric precipitation acidity. If gasoline burns under conditions of oxygen shortage and high temperatures, 3,4-benzpyrene (C₂₀Hi₂) is produced which is a substance having carcinogenic properties. At the stage of fuel ignition, and even more so in starting engine operation or running an engine at no load, that is to say, under excess oxygen conditions, there takes place the synthesis of aldehydes (R_xCHO), which have a narcotic action on the central nervous system. A harmful effect of the chemicals, which are forming in the exhaust gases during the operation of internal combustion engines, is manifested not only in humans but also extends to the entire environment.

The processes of combustion, heat generation and, therefore, fuel consumption and the emissions of harmful substances with the exhaust gases of internal combustion engines are affected, most of all, by the organization of mixing processes. A promising method for reducing fuel consumption and the emissions of harmful substances with the exhaust gases of spark-ignition engines is the use of fuel direct injection along with fuel-air mixture stratification this being especially suitable for two-stroke engines.

The performance of the stratified charge engine is greatly affected by the nature of mixing and combustion processes, by the composition of the fuel-air mixture, which is characterized by the excess air factor, α

where G_aj_r is the air mass;

G_fuei is the fuel mass;

£_Q is the theoretically required air amount for the complete combustion of fuel, and by the disposition of the volume of the fuel-air mixture within the combustion chamber with respect to an ignition source which is spark-plug electrodes. At part loads, a proper organization of mixing and combustion process running at an efficient fuel-air mixture stratification is ensured when, at the time of ignition, the volume, which surrounds the spark plug, and the spark plug gap are charged with an enriched, highly inflammable fuel-air mixture (α=0.8 to 0.9), and the rest of the combustion chamber receives the air (α-→oo). At maximum loads, a uniform distribution of the fuel-air mixture (α ~ 1) throughout the combustion chamber should be ensured.

Fuel-air mixture quality depends on the method of organization of mixing processes. Known in the art are three types of internal mixing: volumetric mixing; volumetric and film mixing; and film mixing. Each of these types has it's own advantages and disadvantages. The most preferred for producing a proper uniform fuel-air mixture, in which the equal number of the molecules of oxygen, nitrogen and other components is located near each of the fuel molecules, is, however, film mixing. In order to ensure an efficient method of film mixing organization, a significant portion of the cyclic feed of fuel injected (over 90%) should be fed onto the combustion chamber surface at an acute angle which ensures the spreading of fuel over the wall in a thin layer while the directed motion of the air charge near the wall should be organized so that an intensive withdrawal of a fuel vapor from the fuel film and a proper mixing of the fuel vapor with an incident air flow are ensured. At the same time, the fuel film should not be destroyed.

The implementation of film mixing is made through an internal mixing organization by means of the direct injection of fuel to the combustion chamber of an internal combustion engine and of the directed motion of the air owing to structural features of the combustion chamber. The internal mixing organization in the combustion chamber depends on a fuel-injection pattern, an average droplet diameter and a fuel-injection pressure. The fuel-injection pattern, as well as the orientation of a fuel injector determines the quality of mixing process running, content formation of the fuel-air mixture,, and the intensity of both ignition and combustion of the fuel-air mixture. At the same time, the internal mixing organization with the employment of the prior art methods of fuel feed causes the complication of the engine design because of necessity to ensure the directed turbulent motion of air this causing the complication of the combustion chamber design. For instance, the employment of turbulence combustion chambers is complicated not only by their shape but also by making use of a special high-temperature material in the uniting port between the head-end volumes. Furthermore, the use of divided combustion chambers increases the heat loss in the cylinder thereby reducing the fuel efficiency of engine. An ignition system is intended for ignition of the fuel-air mixture in the exactly set point of time. In spark-ignition engines, combustion is initiated by an electric spark, i.e., by an electric-spark discharge produced between the spark plug electrodes. To enable an ignition spark to occur, the voltage applied between the spark plug electrodes should increase abruptly to produce a high-voltage electric arc. Once the spark discharge has occurred, the fuel- air mixture located between the spark plug electrodes may be ignited at any point of this phase.

The content of the fuel-air mixture is an important parameter of its ignition which should be within the inflammability range that corresponds to the excess air factor α=0.4- 1.2. An overrich fuel-air mixture (α <0.4), and as well as the ingress of fuel in a liquid phase to the spark-plug gap may bridge the spark-plug gap and thereby bring about the deterioration of spark discharge parameters or even the complete termination of spark formation which, in turn, results in failure of the fuel-air mixture to ignite.

At the same time, to provide a reliable, efficient operation of the engine and to prevent the toxicity of exhaust gases from increasing, it is highly desirable to ensure the leak-tightness of the spray tip of the injector because the spray tip of the injector is exposed to hot gases this resulting in the distortion of its seal faces. This, in turn, may result in a dribbling injector, the disturbance of fuel spray cone formation processes, reduction in mixing and combustion efficiency and further failure of the spray tip.

Hence, there remains the need for en efficient method of mixing and combustion in the combustion chamber of an internal combustion engine which would ensure high power, fuel efficiency and environmental performance, as well as the need for creation of a spark-ignition direct-injection stratified charge internal combustion engine to carry out said method of mixing in the combustion chamber.

Ukrainian patent No. 60,614 discloses a method of mixing in the combustion chamber of a spark-ignition direct-injection internal combustion engine wherein the fuel-air mixture is ignited by a spark plug with electrodes, between which a spark plug gap is provided, the method comprising: the injection, in the compression stroke, of fuel in the form of a cone-shaped spray to the combustion chamber charged with air, fuel spraying onto the surface of the combustion chamber disposed in the cylinder head; and the organization of air charge motion. The internal combustion engine comprises a cylinder; a cylinder head; a piston with a piston head which defines, along with the cylinder head, a combustion chamber which is offset with respect to the cylinder axis and disposed above an exhaust port; and a displacer, wherein the internal surfaces of the cylinder head being concave surfaces and forming a surface of the displacer, which surface is parallel to the piston head, and a surface of the combustion chamber, which are separated by a throat; a spark plug with electrodes between which electrodes a spark plug gap is provided; a fuel injector with a spray tip installed in a cylinder sidewall. The axis of a cone-shaped fuel spray coincides with the axis of the fuel injector, wherein the cone spray reaches the surface of the combustion chamber producing a fuel film on said surface of the combustion chamber near the spark plug electrodes. At the end of the compression stroke, the air flowing to the volume of the combustion chamber forms over the fuel film, an air whirl, which rotates in parallel with the plane of symmetry of the combustion chamber and at the periphery whereof the fuel-air mixture is produced becoming leaner toward the center of the combustion chamber. A disadvantage of the described method of mixing in the combustion chamber of a internal combustion engine, as well as disadvantages of fuel-air mixture combustion are that, owing to the offset of the combustion chamber with respect to the cylinder axis, the air whirl rotates in parallel with the plane of symmetry of the combustion. This results in a one-side running of the fuel-air mixture flow on the spark plug electrodes this, in turn, resulting in a non-uniform distribution of the fuel-air mixture relative to the spark plug electrodes. Later, once the fuel-air mixture is ignited, owing to this, a flame front is distributed non-uniformly within the volume of the combustion chamber. As a result, at part loads, the path of the flame front is extended this resulting in increase in burning process time and reduction in the maximum power, increase in fuel consumption and in the toxicity of the exhaust gases. Moreover, as a result of such asymmetric arrangement of the combustion chamber with respect to the plane of symmetry of the cylinder and, accordingly, with respect to scavenging ports, the air charge leaving scavenging ports interacts with the whirl of the fuel-air mixture one-sidedly this contributing additionally to the non-uniformity of the content of the fuel-air mixture and of its distribution within the volume of the combustion chamber.

Known in the art is also a method of mixing in the combustion chamber of an internal combustion engine disclosed in United States patent No. 3,420,216, the method comprising: the injection, in the compression stroke, of fuel in the form of a cone-shaped spray to the combustion chamber charged with air, fuel spraying onto the surface of the combustion chamber disposed in the pison body; and the organization of air charge motion. Fuel is sprayed to the zone of a recess made at the surface of the combustion chamber.

A disadvantage of the described method is a one-side running of the fuel-air mixture flow on the spark plug electrodes which, in turn, results in a non-uniform distribution of the fuel-air mixture relative to the spark plug electrodes. Later on, once the fuel-air mixture is ignited, as a result of this, the flame front is distributed non- uniformly within the volume of the combustion chamber. As a result, at part loads, the path of the flame front is extended this resulting in increase in burning process time and reduction in the maximum power, increase in fuel consumption and in the toxicity of the exhaust gases. Moreover, the air without fuel particles remains in the volume of the combustion chamber between the surfaces of the displacer of the cylinder head and the piston head this resulting in an additional loss of power, which can be attained. The disadvantages of the above described engineering solution also include the complication of the combustion chamber design, increase in the piston weight that reduces the engine speed. The arrangement of the fuel injector in the cylinder head also deteriorates the performance reliability of the spray tip of the injector.

The most similar to the internal combustion engine in accordance with this invention is a spark-ignition direct-injection stratified fuel-air charge internal combustion engine disclosed in British patent No. 2,215,398, the engine comprising: a cylinder; a cylinder head; a piston with a piston head which piston defines, along with the cylinder head, a combustion chamber, wherein the internal surfaces of the cylinder head are concave surfaces and form the surfaces of the combustion chamber; a spark plug with electrodes between which there is a spark plug gap; a fuel injector with a spray tip installed in a cylinder sidewall. The spray tip of the fuel injector is configured as turbulent.

A disadvantage of the described engineering solution is that, during fuel injection into the combustion chamber to the zone where the spark plug is disposed, the injector produces a turbulent motion of fuel this resulting, at the beginning of formation of the fuel spray cone and during its motion, in an intensive mixing of sprayed fuel particles with the air charge this contributing to the formation of a mixed fuel-air mixture throughout entire volume of the fuel spray cone. At the same time, in the area of the generator of the spray cone, an intensive mixing of fuel particles with the surrounding air charge also takes place this resulting in increase in the fuel-air mixture volume, and, at part loads, upon ignition and during further burning, the fuel- air mixture volume increases substantially to the volume of the combustion chamber this reducing the degree of fuel-air charge stratification (the ratio of the air volume without fuel vapor to the head-end volume), this being described by formula _ 1 a V „ _ V - —_ * c V " mix — _ 1 V I M'-v — X ""mix

where V₀ is the head-end volume;

V_mix is the fuel-air mixture volume;

α_mi_X is the excess air factor for the fuel-air mixture volume; and

α_c is the excess air factor for the head-end volume,

and, as a result, the optimum range of engine operation in terms of fuel consumption and the minimum emissions of harmful substances with the exhaust gases will be strictly limited. Besides, during further burning of the fuel-air mixture that is leaning, the velocity of flame front motion decreases. Moreover, the leaning of the fuel-air mixture at the periphery, far from the location where the spark plug electrodes are disposed, facilitates the formation of peroxides this resulting in the occurrence of knocking combustion and engine destruction.

The common disadvantage of the prior art methods of mixing in the combustion chamber of an internal combustion engine is, thus, an insufficiently efficient stratification of both volume and content of the fuel-air mixture within the volume of the combustion chamber this reducing the efficiency of combustion process running. More particularly, the formation of fuel-air mixture volumes separated by the air charge along the path of flame front motion, a non-uniform distribution of the fuel-air mixture volume with respect to the location where the spark plug electrodes are disposed increase the maximum path and time of flame front motion, a non-uniform admission of air to the burning zone with a different excess air factor α likewise reducing combustion efficiency. In the upshot, the indicated efficiency (ηi) reduces which shows what portion of the chemical energy of fuel admitted to the displacement volume of the engine is converted upon combustion to the useful work of gases this characterizing the degree of perfection of operation process organization. At the same time assessment and comparison of ηj of a two-stroke engine with carburation and direct fuel injection should be made taking to account only that fuel that remains in the cylinder after the closure of devices of the timing system:

where L₁ is the intra-cylinder indicated work of gases per cycle;

Q_tf is the low available heat value of fuel;

Gf_uei._c is the amount of fuel that remains in the cylinder per cycle;

Gf_uei._tr is the amount of transit fuel lost (for instance, in scavenging the cylinder);

Z is the coefficient that takes into account the fuel loss (for instance, in scavenging the cylinder) and is equal to the ratio of the amount of transit fuel lost (Gfy_ei a) to the amount of fuel (Gf_ueι,_c), which remains in the cylinder upon completion of gas exchange processes.

An object of this invention is to develop an efficient method of mixing in the combustion chamber of an internal combustion engine, which would be simple and reliable and would make it possible to improve the economic performance of the engine and to limit emissions of harmful substances with its exhaust gases.

Another object of this invention is to provide a spark-ignition direct-injection stratified fuel-air charge internal combustion engine, which, owing to its configuration, makes it possible to practice efficiently the above described method of mixing in the combustion chamber of an internal combustion engine with the assurance of all of the disadvantages of said method.

The object set is achieved by that there is provided a method of mixing in the combustion chamber of a spark-ignition direct-injection stratified fuel-air charge internal combustion engine wherein the fuel-air mixture is ignited by a spark plug with electrodes, between which a spark plug gap is provided, the method comprising: the injection, in the compression stroke, of fuel in the form of a cone-shaped spray to the combustion chamber charged with air, fuel spraying onto the surface of the combustion chamber disposed in a cylinder head; and the organization of air charge motion. At the same time, the fuel is injected and sprayed so that a cone-shaped fuel spray is produced which cone-shaped fuel spray consists of a cone-shaped body of the spray cone having the excess air factor ot_b. _Sp_ray and a cone-shaped cavity within the body of the spray cone having the excess air factor α_c. _spray. Besides, the motion of air charge is directed uniformly on all the sides along the combustion chamber surface towards the spark plug electrodes. The cone-shaped fuel spray is directed so that the spark-plug gap is located inside the cone-shaped cavity this alows to prevent the bridging of the spark-plug gap and the deterioration of spark discharge parameters, and even the complete termination of sparking from occurring. It will be also appropriate when the fuel is sprayed to the flame body in the form of coarsely divided droplets, which create a fuel film on the surfaces of the combustion chamber around the spark plug electrodes.

In the method in accordance with this invention, the combustion chamber is symmetric and disposed within the cylinder head symmetrically to the cylinder axis. As the piston moves from the bottom top center to the bottom dead center to the top dead center, the symmetric surface of the displacer along with the parallel surface of the piston head provides air charge motion over the combustion chamber surface from the periphery to the top thereof. The spark plug is disposed at the top of the combustion chamber. Such a disposition of the spark plug ensures, during combustion, a uniform propagation of the flame front within the volume of fuel-air mixture, alleviates conditions precedent of knocking combustion, and ensures a uniform distribution of pressure exerted by gases on the piston. As a result, heat and mechanical losses are reduced. Preferably, the injector is disposed in the cylinder wall. Such a disposition of the injector reduces the exposure of the injector spray tip to hot gases since it is located out of the high temperature zone. The fuel is injected in the form a hollow cone-shaped fuel spray the axis whereof is oriented at the central electrode of the spark plug this making it possible to prevent the bridging of the sparkplug gap and the deterioration of spark discharge parameters, and even the complete termination of sparking from occurring. In order to make stratification deeper, the evaporability of fuel particles during injection should be reduced. It will be also appropriate when the fuel is injected in the flame body in the form of coarsely divided droplets, which create a fuel film on the combustion chamber surfaces around the spark plug electrodes. At the same time it is necesary that more than 90% of the fuel reaches the combustion chamber surface. As a result, an annular fuel film is created on the combustion chamber surface located substantially symmetrically about to the central electrode of the spark plug. This allows fuel vapor to be retained near the combustion chamber surface. Along the combustion chamber surface, air charge motion is produced. At the time of ignition, the air charge moves on all the sides simultaneously to the spark plug electrodes. During this process, the fuel-air mixture is produced which is distributed in a uniform layer over the combustion chamber surface and likewise moves to the spark plug electrodes.

Later on, such an organization of fuel-air mixture stratification makes it possible, when fuel is evaporated out of the combustion chamber surfaces and the fuel vapor is mixed with the air charge that moves and is directed over the combustion chamber surface to the spark plug electrodes, to produce, near the combustion chamber surface and between the spark plug electrodes, the volume of a homogenous, well- mixed enriched fuel-air mixture with the excess air factor α=0.8 to 0.9. At the same time, the volume of the fuel-air mixture will not be substantially mixed with the air volume in any other portion of the head-end volume. The total excess air factor in the volume of the combustion chamber may reach α=6. Such an operation process organization would make it possible to provide proper fuel-air mixture stratification in the engine cylinder.

After ignition, during the combustion process running, the flame front and the fuel-air mixture move towards each other. At the same time, the fuel-air mixture moves from the outer perimeter of the fuel-air mixture ring towards the spark plug electrodes this ensuring, during the propagation of the flame front within the volume of fuel-air mixture, which moves towards the flame front, combustion efficiency improvement. Upon propagation of the flame front close to the combustion chamber surface, said surface is heated as a result of exposure to the flame front and, at the following stroke and fuel spraying onto said surface, an intensive vaporization of the fuel film is ensured. In the expansion stroke, the leavings of the fuel-air mixture and the flame front that propagates wherein are directed to the volume between the surface of the displacer and piston head leaving combustion products after flame front passage. Combustion process intensification in the expansion stroke takes place owing to the flow of air charge from the center of the combustion chamber to the volume between the surface of the displacer and piston head to the zone of burning due to pressure difference in these volumes of the combustion chamber. This, in turn, increases the total pressure of gases on the piston (indicated pressure) this improving the useful work of gases in the expansion stroke. Afterburning of the combustion products takes place in the cylinder volume where oxygen excess facilitates a substantially complete combustion of fuel particles that remain. The method in accordance with this invention does not produce fuel-air mixture volumes separated by the air charge along the path of flame front motion, prevents a non-uniform distribution of the fuel-air mixture volume with respect to the spark plug electrodes, and ensures the minimum path and time of flame front motion. All these contribute to combustion process intensification. A uniform admission of air to the zone of burning provides the same and permanent fuel-air content of the fuel-air mixture when combusted enriched with the excess air factor (α=0.8 to 0.9) this also improving combustion efficiency. In the upshot, the indicated efficiency at maximum and part loads is increasing this resulting in reduction in fuel consumption and emissions of harmful substances with the exhaust gases are also diminished.

In one preferred embodiment of the method in accordance with this invention, the body of the spray cone has the excess air factor α_b. _spray between 0.01 and 0.4. The excess air factor α_b. _spray of less than 0.01 corresponds to a substantially liquid phase where a portion of the volume of the fuel-air mixture having such fuel-air content occupies a space near the vertex of the fuel spray cone which vertex is located next to the spray tip of the injector with a minimum amount of air admitted to the fuel spray cone. When the fuel is injected to the combustion chamber charged with air, however, interaction between surface tension forces at an uneven surface of the jet and aerodynamic resistance forces in the flame front on the part of the air charge takes place. Fuel droplets, which are being injected, are starting to break into pieces thereby increasing the volume of fuel spray and the amount of air admitted thereto this resulting in leaning the fuel-air mixture within the flame body. At the excess air factor α _b. _spray of over 0.4, undesirable leaning in the volume of the fuel-air mixture (α>0.9) may occur at the time of ignition that would have a negative effect on the processes of ignition, further combustion and engine performance.

In another preferred embodiment of the method in accordance with this invention, the cone-shaped cavity of the spray cone has the excess air factor α _b. _spray from 1.5 to ∞. At the excess air factor α_a, _spray of less than 1.5, overriching in the volume of the fuel-air mixture (α<0.8) occurs at the time of ignition that will reduce the intensity of combustion process running.

At the same time, to provide an efficient film mixing and to ensure that more than 90% of the fuel reaches the combustion chamber surface, the fuel is sprayed in the form of coarsely divided droplets this enabling a fuel film to be produced at the interior surface of the combustion chamber around the spark plug electrodes.

Another object set is achieved by that there is provided a spark-ignition direct- injection stratified fuel charge internal combustion engine, the engine comprising: a cylinder; a cylinder head; a piston with a piston head, wherein piston defines, along with the cylinder head, a combustion chamber disposed symmetrically about the cylinder axis and a displacer, wherein the internal surfaces of the cylinder head being concave surfaces and forming the surface of the displacer, which is parallel to the piston head, and an interior surface of the combustion chamber, which surfaces are separated by a throat; a spark plug with electrodes between which a spark plug gap is provided; a fuel injector with a spray tip installed in a cylinder sidewall; wherein the fuel injector being configured to be capable of producing a cone-shaped fuel spray consisting of a body of the spray cone in the form of a cone bounded by its generator and an external divergence angle α, and of a cone-shaped cavity in the body of the spray cone bounded by its generator and an internal divergence angle β, wherein the injector being installed so that the spark-plug gap is located inside the cone-shaped cavity of the spray cone. Such a design of the internal combustion engine in accordance with the invention makes it possible to prevent the bridging of the sparkplug gap from occurring which may result in the deterioration of spark discharge parameters, and even in the complete termination of sparking. Moreover, due to a simple and reliable configuration of the engine in accordance with the invention as described above, an efficient implementation of the method in accordance with this invention of fuel feed to the combustion chamber of the engine becomes possible, as a result whereof the film mixing process takes place in a zone surrounding the spark plug with electrodes, between which a spark-plug gap is provided, this preventing the spark-plug gap from being bridged during the process of injection because of its location within the cone-shaped cavity of the fuel spray cone. Later on, this will make it possible, in turn, when fuel is vaporized out of the combustion chamber surfaces and the fuel vapor is mixed with the air charge that moves and is directed along the combustion chamber surface to the spark plug electrodes, to produce, near the combustion chamber surface and between the spark plug electrodes, the volume of a homogenous, well-mixed enriched fuel-air mixture with the excess air factor α=0.8 to 0.9 and, inside the combustion chamber, a relatively clean air. Such an organization of operation process facilitates the formation of deep proper fuel-air mixture stratification in the head-end volume at part loads. A high quality of such stratified fuel-air mixture would make it possible, in turn, to improve economic and environment performance of the engine and to increase engine power at maximum loads.

Preferably, the fuel injector is configured with a changeable external divergence angle α of the fuel spray cone within a range from 5° to 80° this making it possible to ensure the most optimum fuel distribution over the interior surfaces of the combustion chamber, to control fuel film evaporation time, and to provide the desired volume and fuel-air content of the fuel-air mixture. The possibility of changing the external divergence angle α of the fuel spray cone at different loads is ensured by change in cyclic fuel feed, in fuel injection pressure, by the valve stroke of the spray tip, and by change in the geometry of the spray tip nose. Such a fuel spray cone may be produced by valve nozzles, pintle nozzles or multijet nozzles. If the external divergence angle α of the fuel spray cone is less than 5°, the spark plug electrodes will then be bridged to each other by liquid fuel and, at the moment of voltage application thereto, no ignition of the fuel-air mixture will take place.

If the external divergence angle α of the fuel spray cone is more than 80° and the generator of the fuel spray cone intersects the cylinder surface, the fuel that has got to the cylinder walls will not participate in the combustion process which will deteriorate greatly economic and environmental performance of the engine.

It is likewise advantageous for the stratified fuel-air mixture organization at part loads such configuration of the engine in which, if engine load is increased from minimum to 60% of the maximum power, the external divergence angle α of the fuel spray cone is increased from α=5° to the value of α at which the generator of the fuel spray cone reaches the throat of the combustion chamber, wherein the fuel spray cone is projected entirely on the surface of the combustion chamber of the engine.

Upone increase of engine load from 60% up to 100% of the maximum power, the external divergence angle α of the fuel spray cone may be increased to α=80° and its generator intersects the surface of the displacer of the combustion chamber, wherein the fuel spray cone being projected partially on the surface of the displacer and partially on the surface of the combustion chamber, i.e., at maximum loads and the maximum divergence of the fuel spray cone, most portion of the surface of the combustion chamber which is located in the cylinder head will be covered uniformly by fuel film. This would make it possible to vaporize the fuel out of the surface during a relatively short time and to organize proper fuel-air mixture. At the same time, the fuel deposited on the surface of the displacer of the cylinder head will be vaporized more intensively because, in the compression stroke, as the piston head approaches to the displacer of the cylinder head, an intensive motion of the air charge is produced between these surfaces and under the fuel film.

In another preferred embodiment of the internal combustion engine, wherein the fuel spray cone has a constant value of the internal angle β this excluding necessity in the complication of the design of the spray tip of the fuel injector. In yet another preferred embodiment, the configuration of the fuel injector is such that, at different loads, the internal angle β of the fuel spray cone may vary from 3° to 45°. The minimum value of the internal angle β=3° ensures the reliable prevention of bridging the spark-plug gap at no load and minimum loads. Increase of the internal angle β to 45° in the event of increase in engine power makes it possible to ensure the constant fuel-air content of the fuel-air mixture (α=0.8 to 0.9) between the spark plug electrodes and in the volume of the fuel-air mixture for the efficient combustion of the stratified fuel-air mixture. As the internal angle β is increased from 3° to 45°, the volume of the fuel-air mixture is increased and the disposition of the mixture volume with respect to the spark plug electrodes at the moment of ignition is controlled.

To ensure a uniform airflow over the combustion chamber surface from its periphery to its top, it is necessary that the area of the displacer of the combustion chamber is between 30% and 60% of the piston head area. At the same time the surfaces of the displacer and piston head extend in parallel with each other. It should be pointed out, that the engine design with the symmetric combustion chamber disposed in the cylinder head symmetrically to the cylinder axis and with the injector installed in the cylinder wall is one of the possible simplest designs that ensures the described above method of mixing in accordance with this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a cross sectional view of the engine and fuel spray cone during fuel injection;

Fig. 2 shows the organization of fuel-air mixture stratification in the compression stroke at part loads;

Fig. 3 shows the organization of fuel-air mixture stratification in the volume of the combustion chamber at the time of ignition at part loads;

Fig. 4 shows flame front propagation when the piston is in the top dead center at part loads. Fig. 5 shows flame front propagation in the expansion stroke at part loads;

Fig. 6 shows the afterburning of combustion products in the expansion stroke before opening exhaust devices of the timing system;

Fig. 7 shows the organization of fuel-air mixture stratification in the compression stroke at maximum loads;

Fig. 8 shows the organization of the distribution of the fuel-air mixture and air charge in the volume of the combustion chamber at the moment of ignition at maximum loads;

Fig. 9 shows flame front propagation when the piston is in the top dead center at maximum loads;

Fig. 10 shows flame front propagation in the expansion stroke at maximum loads.

Fig. 1 is a cross sectional view of the internal combustion engine in accordance with this invention and^' fuel spray cone during fuel injection. The internal combustion engine in accordance with this invention is a spark-ignition direct-injection internal combustion engine and comprises a cylinder 1 ; a cylinder head 2; a piston 3 with a piston head which defines, along with the cylinder head 2; a combustion chamber 4 which is disposed symmetrically about the axis Z-Z of the cylinder 1; and a displacer, internal surfaces 2a and 2b of the cylinder head 2 being concave surfaces and forming a surface of the displacer 4a which is parallel with the piston 3 head, and a surface of the combustion chamber 4, which are separated by a throat 4b; a spark plug 5 with electrodes 6 between which there is a spark plug gap 7; a fuel injector 8 with a spray tip 9 installed in the sidewall of the cylinder 1. The combustion chamber 4 is disposed symmetrically to the axis Z-Z of the cylinder 1; and the surface 2a of the combustion chamber 4 is separated of the surface 2b of the displacer 4a by a throat 4b. The fuel injector 8 is configured capable of producing a cone-shaped fuel spray 10, which consists of a body 11 of the spray cone 10 in the form of a cone limited by its generator and an external divergence angle α and of a cone-shaped cavity 12 in the body 11 of the spray cone 10 limited by its generator and an internal divergence angle β, wherein the injector 8 being installed so that the spark-plug gap of the spark plug 5 is located inside the cone-shaped cavity 12 of the spray conelO.

Fig. 2 shows the process of the organization of fuel-air mixture stratification in the compression stroke at part loads. In this figure there are shown a fuel film 13, a fuel vapor 14, a fuel-air mixture 15 and an air charge 16, which are in the combustion chamber.

Fig. 3 shows the process of the organization of fuel-air mixture stratification in the volume of the combustion chamber at the moment of ignition at part loads. All elements are designated by the reference numbers, which are similar to those in Fig. 1 and Fig.2

Fig. 4 shows a flame front propagation process when the piston is in the top dead center at part loads. The figure shows a flame front 17 propagating across the volume of the combustion chamber, and combustion products 18.

Fig. 5 shows a flame front propagation process in the expansion stroke at part loads. All the elements are designated by the reference numbers, which are similar to the preceding figures.

Fig. 6 shows the process of the afterburning of combustion products in the expansion stroke before opening exhaust devices of the timing system. All the elements are designated by the reference numbers, which are similar to the preceding figures.

Fig. 7 shows the process of the organization of fuel-air mixture stratification in the compression stroke at maximum loads. All the elements are designated by the reference numbers, which are similar to the preceding figures.

Fig. 8 shows the process of the organization of the distribution of the fuel-air mixture and air charge in the volume of the combustion chamber at the moment of ignition at maximum loads. All the elements are designated by the reference numbers, which are similar to the preceding figures.

Fig. 9 shows flame front propagation process when the piston is in the top dead center at maximum loads. All the elements are designated by the reference numbers, which are similar to the preceding figures.

Fig. 10 shows flame front propagation process in the expansion stroke at maximum loads. All the elements are designated by the reference numbers, which are similar to the preceding figures. The method of mixing in the combustion chamber of an internal combustion engine is carried into effect as follows:

In mixing in the compression stroke and during the motion of the piston as the crankshaft turns from 200 degrees to 355 degrees after the top dead center, the fuel is injected to the symmetric combustion chamber 4 charged with air having the throat 4b and the displacer 4a, which chamber is disposed symmetrically to the axis Z-Z of the cylinder 1 in the cylinder head 2, by means of the injector 8 installed in the sidewall of the cylinder 1 not at the intersection of a scavenging port (not shown) of a two-stroke sleeve-valve engine (Fig. 1); wherein the spray tip 9 of the injector 8 produces the cone-shaped fuel spray 10 consisting of the body 11 of the spray cone 10 in the form of a cone and the cone-shaped cavity 12 in the body 11 of the spray cone 10 with the axis of symmetry (E-E) coinciding with the plane of symmetry of the cylinder 1 in which the axis (Z-Z) of the cylinder (I)₅ which comes through the axis (Z-Z) of the spark plug 5 disposed at the top of the combustion chamber 4, wherein the axis (E-E) of the spray cone 10 intersecting the axis (Z-Z) of cylinder 1 at the end face of the central electrode 6 of the spark plug 5. The spray cone 10 is sprayed through the throat 4b of the combustion chamber 4 so that the spark plug gap 7 of the spark plug 5 is inside the cone-shaped cavity 12 in the body 11 of the spray cone 10. Upon reaching the internal surfaces 2a and 2b of the combustion chamber 4, the spray cone 10 does not interact with air flows admitted from the scavenging ports for the fuel injector 8 is installed out of the scavenging port and the trajectory of air flow motion does not intersect with direction of motion of the spray cone 10, wherein the intensity of the air flows being decreased before the time of the beginning of injection and, as a result, the spray cone 10 produces, in the projection on these surfaces 2a and 2b of the combustion chambers 4 before the time of ignition (as the crankshaft turns from 220 degrees to 355 degrees after the top dead center), a ring around the electrodes 6 of the spark plug 5 in the form of the fuel film 13 (with the excess air factor α=0) above which, as it vaporizes, the fuel vapor 14 (α=0) is produced (Fig. 2, 7). Upon mixing of the top layer of the fuel vapor with air, the fuel-air mixture 15 (α=0.01 to 0.9) is produced; accordingly, the electrodes 6 of the spark plug 5, which are not flooded with the liquid fuel, are positioned in the center of the ring. At the same time at the end of the compression stroke (as the crankshaft turns at an angle of more than 300 degrees after the top dead center), from the volume located under the displacer 4a of the cylinder head 2 and the piston 3 head, there is organized an intensive displacement of the flow of the air charge 16 and the fuel-air mixture 15, which is produced upon mixing of the air and fuel, to the volume of the combustion chamber 4 through the throat 4b. The displaced flow of the fuel-air mixture 15 moves, while interacting with the axial air charge 16 directed along the axis (Z-Z) of the cylinder 1 by the piston 3, above the surface 2a of the combustion chamber 4 moving the fuel-air mixture 15 from the external perimeter of the ring to the top of the combustion chamber 4 where the electrode 6 of the spark plug 5 are located. At the time of ignition (Fig. 3, 8) (as the crankshaft turns from 40 degrees to 5 degrees before the top dead center), the volume of the combustion chamber 4 is divided to the volume of an enriched fuel-air mixture 15 (α=0.8 to 0.9) disposed near the surface 2a of the combustion chamber 4 and in spark plug gap 7 of the spark plug 5 and the volume of the air charge 16 with α=∞, disposed in the center of the combustion chamber 4. Such an unmixed stratification of the fuel-air mixture 15 and the air charge 16 (α=oo) is organized thanks to that the combustion chamber 4 is of a symmetric shape and that, at the end of the compression stroke, the air charge 16 (α=co) presses uniformly the fuel-air mixture 15 (α=0.8 to 0.9), which was produced against the surfaces 2a of the combustion chamber 4 towards the electrodes 6 of the spark plug 5. At the same time there also remains a substantially pure air charge 16 (α=ω) unmixed with the fuel vapor 14 (α=0) in annular volumes between the surface 2b, the throat 4b of the combustion chamber 4 defined by the beginning of the surface 2b and the surface of the piston 3 head. Since, firstly, fuel injection at part loads is provided by a low pressure

MPa to 5 MPa) and the velocity of the motion of the fuel spray cone (V_max<60 m/s) and the gas temperature within the cylinder (t∞80°C) ensure the formation of large size fuel droplets in the fuel spray cone 10 (the average diameter of fuel droplets is d_av = 500 μm), that reduces greatly the intensity of vaporizing fuel particles during the motion of the fuel spray cone 10. As a result, about 1% of the mass of the cyclic feed of fuel injected is vaporized in the total volume of the cylinder. Secondly, during fuel injection as the crankshaft turns from 220 degrees to 355 degrees after the top dead center with increase in engine load, when the external divergence angle α of the fuel spray cone 10 is increased from α =5° to the value of α, at which the generator of the fuel spray cone 10 reaches the throat 4b of the combustion chamber 4, and the excess air factor ^_{b spray} in the body 11 of spray cone 10 is increased from 0.01 to 0.4 and the excess air factor α_a. _spray in the cone-shaped cavity 12 of the spray cone 10 enhances from 1.5 to oo, the spray cone 10 is projected entirely on the surface 2a of the combustion chamber 4 of the engine and does not interact with the air flows admitted from the scavenging ports. At the same time, the spray cone may have both constant value and value varying from 3° to 4.5° of the internal divergence angle β, and the fuel injector may comprise a valve spray tip, multijet spray tip or a pintle spray tip. As a result, about 1% of the mass of the cyclic feed of fuel injected is vaporized in the total volume of the cylinder. Thirdly, once the last fuel particles located in the tail of the fuel spray cone 10 have reached the surface 2a of the combustion chamber 4 (Fig. 1), the motion of the air charge 16 in the combustion chamber 4 presses the fuel-air mixture 15 produced after vaporizing the fuel film 13 and mixing the fuel vapor 14 with the air charge 16 at their interface (Fig. 2) against the surface 2a of the combustion chamber 4 and does not allow it to be mixed with the air charge 16 located in the center of the combustion chamber 4 (Fig. 3). Such an unmixed stratification of the fuel-air mixture 15 and the air charge 16 at the time of ignition is organized thanks to that the combustion chamber 4 is of a symmetric shape and that, upon interaction of the axial motion and radial motion, the air charge 16 (α→∞), at the end of the compression stroke, presses uniformly the fuel-air mixture 15 (α=0.8 to 0.9) formed against the surfaces 2a of the combustion chamber 4 towards the electrodes 6 of the spark plug 5 (Fig. 3). This occurs as a result of the fact that the surface of the piston 3 head located under the displacer 4a is parallel thereto and forms, in the section of the plane of symmetry which comes through the axis (Z-Z) of the cylinder, an acute angle with the plane that coincides with the mating face of the cylinder head 2, as well as due to the fact that the angle between the surface 2b of the displacer 4a and the surface 2a of the combustion chamber 4 exceeds 90°. With such a configuration of the combustion chamber 4, the radial air flow displaced from under the displacer 4a moves, while interacting with the axial air charge directed along the axis (Z-Z) of the cylinder 1 by the piston 3, above the surface 2a of the combustion chamber 4. At part loads of the engine from minimum up to 60% of the maximum power, the total excess air factor in the volume of the combustion chamber 4 may reach α=6.

At the time of ignition (Fig. 8) (as the crankshaft turns from 40 degrees to 25 degrees before the top dead center) at higher loads of the engine from 60% to 100% of the maximum power, the volume of the combustion chamber 4 is charged with a well- mixed enriched fuel-air mixture 15 (α=0.8 to 0.9). The fuel-air mixture 15 (α=.8 to 0.9) is also disposed in the volume between the surface of the displacer 4a and the piston 3 head, but the air charge 16 having α-→∞ is disposed near the cylinder 1 walls. As load is increased, the total excess air factor in the volume of the combustion chamber 4 is reduced and, at the maximum load, is equal to the stoichiometric ratio (α=l). The formation of such a method of the organization of the process of mixing with fuel-air mixture stratification is organized owing to the fact that, when the engine load is increased, the fuel is injected at a pressure P_inj=5 MPa to 15 MPa as the crankshaft turns from 220 degrees to 355 degrees after the top dead center and the fuel spray cone 10 is projected partially on the surface 2a of the combustion chamber 4 and partially on the surface 2b of the displacer 4a the area whereof is from 30% to 60% of the area of the piston 3 head. At the same time to produce a homogenous composition of properly mixed fuel-air mixture 15, most fuel is directed onto the surface 2b of the displacer 4a by means of increase in the external angle α of the fuel spray cone 10 to α=80° when its generator intersects the surface 2b of the displacer 4a of the combustion chamber 4 and the excess air factor α_b sp_ray is increased from 0.01 to 0.4 in the body 11 of the spray cone 10 and by means of increase in the divergence of the internal divergence angle β of the fuel spray cone 10 from 3° to 45°; at that, the excess air factor α_{a spray} in the cone-shaped cavity 12 of the spray cone 10 is decreased from ∞ down to 1.5.

Following ignition, during combustion process running at the end of the compression stroke (as the crankshaft turns from 40 degrees to 0 degrees before the top dead center) and at the beginning of the expansion stroke (as the crankshaft turns from 0 degrees to 10 degrees after the top dead center) (Fig. 4, 9), the flame front 17 propagates from the electrodes 6 of the spark plug 5 across the volume of the fuel-air mixture 15 (α=0.8 to 0.9) that moves towards it as a result of its propping up by the flow of the air charge 16 (α=oo) directed from the volume of the combustion chamber located under the surface 2b and above the piston 3 head leaving the combustion products 18 upstream the flame front 17. In the expansion stroke, as the piston 3 moves from the top dead center to the bottom dead center (as the crankshaft turns from 10 degrees to 60 degrees after the top dead center) (Fig. 5, 10), the leavings of the fuel- air mixture 15 and flame front 17 that propagates across it are directed, through the throat 4b, to the annular volume between the surface 2b and the piston 3 head as a result of a sharp increase in the volume and pressure reduction in this volume where an intensive admission of air to a zone of turbulent burning takes place. After this, the afterburning of the combustion products 18 occurs in the head-end volume (Fig. 6): in the volume of the cylinder 1 and in the volume of the combustion chamber 4 till the opening of exhaust devices of the timing system (as the crankshaft turns from 60 degrees to 80-180 degrees after the top dead center). In the method in accordance with the present invention as described above (Fig. 1), the fuel is injected through the spray tip 9 of the injector 8 as the spray cone 10 in the form of a hollow cone which has, in its symmetrical section through the generator, the external divergence angle α and internal angle β that separates the fuel-air mixture volume in the body of the spray cone 10 from the cone-shaped internal cavity 12, wherein depending on the power conditions of the engine and cyclic feed of fuel, the external angle α is changed from the minimum angle (αi), when the fuel spray cone moves through the throat 4b and is projected entirely on the surface 2a of the combustion chamber 4 of the engine, to the maximum angle (α₂) when the fuel spray cone 10 is projected partially on the surface 2a and partially on the surface of the displacer 4a of the combustion chamber 4 of the engine. Under all of the power conditions of the engine and in a varying cyclic feed of fuel, the internal divergence angle β may remain constant or vary from its minimum value to its maximum_, value, wherein the fuel spray cone 10 reaches the surfaces of the combustion chamber 4 producing the fuel film 13, which if projected on these surfaces (2a and 2b) comprises a solid ring the external perimeter whereof is bounded by the generator of the fuel spray cone 10 with the external angle α while the internal perimeter is bounded by the generator of the cone-shaped cavity 12 of the fuel spray cone 10 with the internal angle β and the electrodes 6 of the spark plug 5 are disposed in the center of said ring. As load and the cyclic feed of fuel are increased in the compression stroke (Fig. 2, 7), to increase the volume of the fuel-air mixture 15 with α=0.8 to 0.9, the fuel is injected (as the crankshaft turns from 200 degrees to 320 degrees after the top dead center) to the combustion chamber 4 at a pressure

MPa to 15 MPa and, as a result of increase in injection pressure, of increase in the concentration of fuel particles, and of displacing the amount of fuel, which is increasing, to the periphery towards the generator of the fuel spray cone 10, the volume of the fuel spray cone 10 and the external divergence angle Ot₁ of the fuel spray cone 10 are increased this resulting in increase in the area of the fuel film 13 at the surfaces 2a and 2b. The maximum external divergence angle α₂ (Fig. 1) of the fuel spray cone 10 till the time of ignition (as the crankshaft turns from 40 degrees to 10 degrees before the top dead center) is limited by the surface of the cylinder 1 and the internal divergence angle β may be increased as loads and the cyclic feed of fuel are increased up to their maximum values, and the maximum value of the angle β is limited by about 45°.

Thus, the invention is represented by an efficient method of mixing in the combustion chamber of a spark-ignition, stratified charge internal combustion engine with producing a fuel film at the surfaces of the combustion chamber around spark plug electrodes. This simple and reliable in service method allows both power and fuel efficiency performance of the engine to be improved and emissions of harmful substances with the exhaust gases to be reduced. Besides, another object of the invention is a spark-ignition direct-injection stratified fuel charge internal combustion engine, which, owing to its configuration, makes it possible to ensure the efficient realization of the method of mixing in the combustion chamber of both two-stroke and four-stroke internal combustion engine with the assurance of all of the advantages of said method as described above.

Claims

1. A method of mixing in a combustion chamber of a spark-ignition direct- injection stratified fuel-air charge internal combustion engine a fuel-air mixture being ignited by a spark plug with electrodes, between which there is a spark plug gap, the method comprising: the injection, in the compression stroke, of fuel in the form of a cone-shaped spray to the combustion chamber charged with air; fuel spraying onto the surfaces of the combustion chamber disposed in a cylinder head; and the organization of air charge motion, characterised in that the fuel is injected and sprayed so that a cone-shaped fuel spray is produced which consists of a cone-shaped body of the spray cone having the excess air factor ot_b, _spray and of a cone-shaped cavity within the body of the spray cone having the excess air factor α_c. _spray the cone-shaped fuel spray being directed so that the spark plug gap is located inside the cone-shaped cavity of the spray cone and the motion of the air charge is directed generally uniformly on all the sides over the combustion chamber surface towards the spark plug electrodes.

2. A method according to claim 1, characterised in that the body of the spray cone has the excess air factor at,. _spray fr°^m 0.01 to 0.4.

3. A method according to claim 1 or 2, characterised in that the cone-shaped cavity of the spray cone has the excess air factor α_b. _spray from 1.5 to ∞.

4. A method according to any of claims 1 to 3, characterised in that the fuel is sprayed in the form of coarsely divided droplets, which produce a fuel film on the surface of the combustion chamber around the spark plug electrodes.

5. A spark-ignition direct-injection stratified fuel-air charge internal combustion engine, the engine comprising: a cylinder; a cylinder head; a piston with a piston head wherein piston defines, along with the cylinder head, a combustion chamber disposed symmetrically to the cylinder axis; and a displacer, at that the internal surfaces of the cylinder head are concave surfaces and form the surface of the displacer, which is parallel to the piston head; and an interior surface of the combustion chamber, which surfaces are separated by a throat; a spark plug with electrodes between which there is a spark plug gap; a fuel injector with a spray tip installed in a cylinder sidewall, characterised in that the fuel injector is configured to be capable of producing a cone- shaped fuel spray consisting of a body of the spray cone in the form of a cone bounded by its generator and an external divergence angle α and of a cone-shaped cavity in the body of the spray cone bounded by its generator and an internal divergence angle β, wherein the injector being installed so that the spark-plug gap is located inside the cone-shaped cavity of the spray cone.

6. An engine according to claim 5, characterised in that the fuel injector is configured with a changeable external divergence angle α of the fuel spray cone within a range from 5° to 80° under various power conditions of the engine.

7. An engine according to claim 6, characterised in that when engine load is increased from minimum to 60% of the maximum power, the external divergence angle α of the fuel spray cone is increased from α=5° to the value of α at which the generator of the fuel spray cone reaches the throat of the combustion chamber, wherein the fuel spray cone is projected entirely on the surface of the combustion chamber of the engine.

8. An engine according to claim 6, characterised in that when engine load is increased from 60% up to 100% of the maximum power, the external divergence angle α of the fuel spray cone may be increased to α=80° and its generator intersects the surface of the displacer of the combustion chamber, wherein the fuel spray cone being projected partially on the internal surface of the combustion chamber and partially on the internal surface of the displacer.

9. An engine according to any of claims 5 to 8, characterised in that the fuel spray cone has a constant internal divergence angle β.

10. An engine according to any of claims 5 to 8, characterised in that the fuel injector is configured with a variable internal divergence angle β of the fuel spray cone within a range from 3° to 45° under various power conditions of the engine.

11. An engine according to any of claims 5 to 1O₅ characterised in that the area of the displacer of the combustion chamber is from 30% to 60% of the piston head area.