RU2216838C2 - Spark plug affording considerable reduction of fuel-air mixture combustion time in internal- combustion engines - Google Patents

Abstract

FIELD: internal-combustion engines using electric fuel ignition. SUBSTANCE: spark plug designed for use in internal-combustion engines has metal body, electrodes, and insulator separating them; length of electrodes protruding to combustion chamber is close to or greater than cylinder radius; plug electrodes are hollow structures with cooling agent such as air passed through them. EFFECT: reduced combustion time of fuel-air mixture; enhanced engine efficiency and economic efficiency 1 cl, 4 dwg .

Description

 The invention relates to internal combustion engines (ICE) with spark ignition.

 In ICE, spark ignition is most commonly used. In most internal combustion engines, electric spark plugs (ESs) are located so that the spark gaps (centers of ignition of the fuel-air mixture) only slightly protrude or do not protrude into the lumen of the combustion chamber. In this case, the distance traveled by the combustion front from the spark gap to the most distant areas of the combustion chamber is maximally large, and the total time of combustion of the fuel-air mixture is longer than the piston stroke. In order to ensure sufficiently complete combustion of the fuel-air mixture and optimal characteristics of the pressure change in the combustion chamber, “leading” ignition is used, in which from the moment of ignition to the moment when the piston reaches top dead center, a force is applied against the rotation of the engine shaft, significantly reducing power and fuel economy ICE. In this regard, reducing the combustion time of the fuel-air mixture is an important technical task. One approach to solving this problem is to shorten the path length of the combustion front of the fuel-air mixture, which is equivalent to reducing its burning time.

 Shortening the path length of the combustion front is achieved in different ways. For example, the use of several (2 or more) "ordinary" ES located in different parts of the same combustion chamber (DE 4001819 (Z2, T9) A1); ISM B.65, 1991, 18, p. 18). The use of 2 or more “ordinary” ES in one combustion chamber, although it reduces the burning time, but in principle it cannot lead to its maximum reduction. This greatly complicates the design of the internal combustion engine.

 Reducing the path length of the combustion front and, consequently, the burning time of the fuel-air mixture can be achieved by using ES, in which the parts of the electrodes protruding into the combustion chamber are significantly elongated compared to "ordinary" ES. In such "elongated" ES, the spark gap is closer to the "remote" areas of the combustion chamber. That is, to the areas located near the edges of the working surface of the piston located in the lower positions.

 An ES has been proposed (GB 1227926 A, 04/15/1971), inside of which, to improve the characteristics of the spark, inductors are built in and in which a pair of thin identical electrodes protrudes quite significantly into the combustion chamber according to the drawing given in the description. This ES can be considered as a prototype based on the large length of the parts of the electrodes protruding into the combustion chamber. However, the invention is not intended to reduce the burning time of the air-fuel mixture, and in the claims, the increased length of the electrodes is not mentioned. In addition, cooling of these elongated electrodes is not indicated, due to which, due to insufficient heat transfer to the wall of the combustion chamber, the electrodes must overheat and ignite the mixture like glow plugs.

 When using ES with electrodes that protrude significantly into the combustion chamber, the problem of their cooling to prevent the effect of ignition from incandescent becomes relevant. If in "ordinary" ES electrodes are cooled by heat transfer to the walls of the combustion chamber, such an cooling may not be sufficient for elongated ES.

 An ES for aircraft turbines is described, in which the ignition electrode is protected from overheating in the combustion chamber by a special metal screen and is cooled by an air stream blowing it from the outside (RU 2136094 C1, 08.28.99). Such a device cannot be used in piston ICEs.

 There is an ES for piston internal combustion engines, in which atmospheric air is supplied to the area between the electrodes in the suction stroke, and in other strokes the return gas flow is blocked by a special valve (GB 223660; ISM, V.102, 1993, 1). In this ES, air is not supplied to cool the electrodes, but to clean them. Moreover, cooling in this way cannot be effective, since air is not supplied to all cycles and is scattered between the electrodes and in the combustion chamber. In addition, such valves are not reliable and do not have sufficient speed.

 An ES is proposed for gas turbines, the ignition electrode of which is cooled by air, blown through the channels located in it and entering the combustion chamber (GB 2213874 A, 12/15/1987). This device can be considered as a prototype of the invention on the basis of cooling by air flowing through it. A similar device is difficult to apply for piston ICEs. Indeed, cooling air alone can enter through the electrode only in the suction stroke, and at the same time, it is required to use an unreliable and inert valve apparatus. Or it requires air supply through the electrode at high pressure, which unnecessarily complicates the design of the internal combustion engine.

 This application proposes an ES device that significantly reduces the burning time of the mixture and in which the cooling problem is solved anew.

 This ES consists of the same structural elements as the "ordinary" ES. She has: 1) a metal case, which is screwed into the wall of the combustion chamber with the help of a thread; 2) metal electrodes, one of which is structurally connected to the metal housing of the candle, and, therefore, to the body (mass) of the engine ("grounded" electrode), and the other electrode serves to supply spark-forming voltage ("active"); 3) an insulator electrically disconnecting said electrodes, the ends of the electrodes protruding into the combustion chamber being separated by spark gaps.

The proposed ES has the following essential features:
1. Parts of the electrodes inside the combustion chamber are much longer than those of widely used ES. These electrodes have a length close to or greater than the radius of the cylinder. Due to this, the spark gap of the proposed ES can be installed in such areas of the combustion chamber, in which when the combustible mixture is ignited, the path of the combustion front to remote areas of the said chamber is significantly shortened. For this reason, approximately the same time decreases and the combustion time of the mixture (Figure 1).

 2. The electrodes of the proposed ES are hollow, optimal in shape, size and cross-sections (for example, tubes). Moreover, these hollow electrodes do not open into the combustion chamber (do not communicate with it). Through the electrodes, in order to prevent overheating and appearance of glowing properties in the candle (ignition of a combustible mixture from hot electrodes) and to optimize its thermal properties, forced supply and removal of air or other cooling agent (Figure 3) from a suitable source of pressure difference is performed.

 Depending on the requirements for the combustion time of the mixture, the length of the electrodes of the electrodes of the given ES protruding into the combustion chambers can be determined for each ICE. These electrodes can be so long that, for example, in piston ICE spark gaps can be located even below the plane passing through the edges of the working surface of the piston, which is in the middle position.

 So that the electrodes of the proposed ES do not interfere with the movement of the piston, its working surface must have an appropriate shape. For example, the working surface may be flat with a relatively small length of the protruding parts of the electrodes of the ES protruding into the chamber. Or, in the case of very long protruding parts of the ES electrodes protruding into the combustion chamber, have a special recess where they are immersed when the piston rises to its upper positions, in particular to its top dead center. That is, at all positions of the piston working surface, its contact with the electrodes protruding into the combustion chamber must be excluded.

 The use of the proposed ES significantly shortens the path length of the combustion front and the burning time of the mixture. Since, as a first approximation, the total burning time of the fuel-air mixture in the combustion chamber is determined by the time that is necessary for the combustion front to propagate from the spark gap to the most "distant regions" of the combustion chamber, shortening this path length proportionally reduces the combustion time fuel-air mixture. Figure 2 shows graphically how much the mileage of the combustion front of the mixture is reduced at different positions of the spark gap, that is, with different lengths of the parts of the electrodes protruding into the combustion chamber (respectively, when the working surface of the piston is broken). It can be seen that for the positions of the spark gap shown in the drawings, the length that the combustion front runs through to the areas of the combustion chamber farthest from this spark gap is significantly shortened (30–50% or even more). We note here that in these cases, the areas farthest from the spark gap areas of the combustion chamber should be considered the area near the location of the edges of the working surface of the piston at the time of opening the exhaust valves. Indeed, by the time the exhaust valves open, the combustion of the air-fuel mixture should basically end, since further combustion becomes ineffective.

 Thus, the presence of the "extended" parts of the electrodes protruding into the combustion chamber of the proposed ES allows ignition of the combustible mixture (with the same completeness of its combustion) much later than when using "ordinary" ES.

 FIG. 1. The location in the combustion chamber of the spark gaps of the proposed and conventional ES.

 1 - wall of the combustion chamber; 2 - the working surface of the piston located at top dead center; 3 - recess in the working surface of the piston.

 A - spark gap of ordinary candles; B and C - options for the location of the spark gap in the proposed "long" ES.

 FIG. 2. Comparison of the longest path lengths of the combustion fronts of the fuel-air mixture in the combustion chamber in the case of the proposed and conventional ES.

 1 - walls of the combustion chamber; 2 - the working surface of the piston located at bottom dead center; 3 - deepening the working surface of the piston; 4 - location of the working surface of the piston at the time of opening of the exhaust valves.

 A, B and C - the location of the spark gaps in the usual and the proposed ES (correspond to Fig. 1). О is the point of the combustion chamber farthest from the spark gap at the piston surface at the moment of opening the exhaust valves.

 The AO segment shows the length of the longest path of the combustion front in the case of a conventional ES; segments BO and BO show the length of the largest path of the combustion front in the case of the proposed ES.

 Figure 3. The device of the proposed ES.

 1 - candle body with thread for mounting in the wall of the cylinder head; 2 - hollow active electrode; 3 - a hollow electrode having electrical contact with the candle body; 4 - an electrode for connecting a spark voltage source; 5 - dielectric insulating active electrode; 6 - spark gap; 7 - the conclusions of the hollow electrodes with an approximate direction of the air flow.

 Shown schematically in FIG. 1 and 2, the contour of the wedge-shaped combustion chamber preserves the proportions of the real combustion chamber of one of the production vehicles with ICE. From Figure 2 it follows that the ratio of BO to AO is 70%, and the ratio of BO to AO is 60%. That is, the mileage of the combustion front from the spark gap to the most distant point of the combustion chamber in the case of the proposed ES is 30 and 40% less than when using a "conventional" ES. Approximately the same amount decreases and the time required for combustion of the fuel-air mixture. In turn, this allows ignition of the fuel-air mixture in piston ICEs much later.

 If we take the duration of effective combustion of the mixture in the cylinder (from the moment of ignition to the moment of opening the exhaust valves) at idle approximately equal to 150 angular degrees, then the proposed ES allows you to shift the ignition point by 45-60 angular degrees later than usual. That is, even at fairly high engine speeds (4000-5000 or more revolutions per minute), it is possible to ignite a combustible mixture after the piston passes the top dead center. With the same completeness of combustion of the mixture. In this case, there is no force directed against the movement of the piston ICE shaft. Consequently, fuel efficiency and ICE efficiency increase. In addition, the speed of the initial increase in pressure in the working cycle increases approximately 2 times, since the propagating combustion front has a spherical shape (and not a hemisphere, as in the case of a conventional candle). Thanks to these essential features of the proposed ES, a significant increase in fuel economy and the efficiency of the internal combustion engine is provided.

 The burning time of the mixture can be reduced even more by using relatively longer electrodes than those shown in FIGS. 1 and 2, with the spark gap being even closer to the “distant” regions of the combustion chambers than shown in the drawing.

 Another way to increase the efficiency of the proposed ES is the use of two or more independent spark gaps in one ES located near the axis of the ES at an optimum distance from each other for this ICE. For example, such an ES can include two hollow "active" electrodes, the spark voltage to which is supplied from independent sources (and optionally simultaneously) and one hollow electrode connected to the "mass" of the internal combustion engine. In this case, the travel time of the combustion front of the mixture can be reduced even more than 2 times, and the rate of increase in pressure in the combustion chamber can increase by about 4 times.

 It is obvious that the electrodes of the proposed ES located in the combustion chamber, due to the long length and insufficient cooling by heat transfer to the wall of the combustion chamber, are subject to overheating. This can lead to the appearance of the proposed ES properties inherent in glow plugs, and premature ignition of the fuel-air mixture. In the proposed ES, to eliminate this negative phenomenon for ICE, the electrodes (hollow, metal, optimal shape and cross-section) are cooled by a cooling agent flowing through them. For example, air from sources of differential pressure in the area of throttle valves. In this way, in the electrodes of the proposed ES, the thermal regime that is most advantageous for the internal combustion engine can be maintained.

 The electrodes of the proposed ES, protruding into the combustion chamber, despite their relatively large length, do not interfere with the movement of the valves. Indeed, these electrodes have relatively small transverse dimensions and can be located in the space located between the zones of movement of the valves. Due to this, the implementation of the proposed engine does not require significant changes in the design of the internal combustion engine.

 The proposed ES opens up a large field for modifications: optimizing the location and design of the spark gap (spark gaps), optimizing the thermal regime and characteristics of pressure changes in the operating cycle, improving performance, changing the ignition moment of the combustible mixture, and much more.

Claims (1)

 An electric spark plug for internal combustion engines, including a metal casing, electrodes and an insulator separating them, characterized in that the length of the electrodes protruding into the combustion chamber is close to or greater than the radius of the cylinder, the spark electrodes being hollow and through them a cooling agent, such as air, is passed for cooling.

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