RU2230912C2 - Electric spark plug for internal combustion engine cooled by air flowing through electrodes and decreasing burning time of fuel-air mixture - Google Patents

Abstract

FIELD: mechanical engineering; internal combustion engines.

SUBSTANCE: invention relates to internal combustion engines in which fuel-air mixture is ignited by electric spark plugs. Invention is aimed at providing effective cooling of spark electrodes thanks to which "long" electrodes can be used deeply projecting into combustion chamber with materially cutting time of burning of fuel-air mixture. As a result, ignition of fuel mixture can be provided after passing of top dead center by piston at complete combustion of mixture. Proposed electric spark plug includes metal sheet and electrodes separated by insulator. Electrodes are hollow, and air other cooling agent is passed through electrodes. Length of parts of electrodes from spark gaps to combustion chamber wall is not greater than 10% of cylinder bore.

EFFECT: reduced consumption of fuel and increased efficiency of internal combustion engine.

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Description

The invention relates to internal combustion engines (ICE), in which the air-fuel mixture is ignited using electric spark plugs (ES).

ES electrodes protruding into the combustion chamber operate under conditions of a very high temperature of the working gases. Therefore, effective cooling of the electrodes is an important technical task. Its optimal solution improves the operating qualities of ES, prevents the appearance of glow plug properties in ES, increases reliability and durability. ES for internal combustion engines are usually designed so that the electrodes protrude slightly into the combustion chamber, as a result of which the centers of ignition of the mixture (spark gaps) are in close proximity to its wall. In this case, sufficient cooling of the electrodes is achieved by heat transfer to the wall of the combustion chamber. However, such a cooling method is not always efficient enough. In addition, it limits the possibility of using other ES designs. For example, with “long” electrodes protruding into the combustion chamber.

Other methods for cooling the electrodes are provided. An ES for piston internal combustion engines is described, in which air enters the area between the electrodes (for cleaning, but not cooling) in the suction stroke, and in other strokes the return gas flow is blocked by a special valve (see UK patent No. 2236360 A, IPC H 01 T 13/40, publ. 04/03/1991). Cooling in this way cannot be effective, because the air is not supplied to all cycles and is scattered between the electrodes. At the same time, such valves do not have sufficient speed.

An ES for gas turbines is described, cooled by air blown through the channels located in the electrodes and entering the combustion chamber (see UK Patent No. 2213874 A, IPC H 01 T 13/16, published on 08.23.1989). This ES is difficult to apply in piston ICEs. Indeed, cooling air alone can enter through the electrode only in the suction stroke. To prevent the reverse flow of gases during the working cycle, it is necessary either to use an unreliable and inert valve apparatus, or to supply air under high pressure, which significantly complicates the design of the internal combustion engine.

The proposed ES consists of the same structural elements as the “ordinary” ES. She has: a metal case, mounted in the wall of the combustion chamber; metal electrodes, one of which is structurally connected to the metal housing of the candle and, consequently, to the body (mass) of the engine (“grounded” electrode), and the other electrode serves to supply voltage igniting the combustible mixture (“active” electrode); an insulator that electrically separates ES electrodes. The length of the parts of the electrodes from the spark gaps to the wall of the combustion chamber is more than 10% of the radius of the cylinder.

The proposed ES has the following significant differences:

1. ES electrodes are hollow, optimal in shape, size and cross-sections (for example, tubes), they do not open into the combustion chamber, and air or another cooler is passed through them for cooling (Fig. 1).

2. The electrodes protrude into the combustion chamber for a length that is more than 10% of the radius of the cylinder (Figs. 3, 4).

Figure 1 is an exemplary design diagram of the proposed ES with one spark gap.

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 (“grounded” electrode); 4 - electrical contact for connecting a spark voltage source; 5 - dielectric insulating active electrode; 6 - spark gap; 7 - the conclusions of the hollow electrodes indicating the air flow.

We emphasize that figure 1 shows only a schematic diagram of the device of the proposed ES. The design of this ES, the shape, construction, length and orientation of the electrodes protruding into the lumen of the combustion chamber and the insulator separating them, the location of the spark gap in the combustion chamber and their number on one ES for each specific type of ICE can be different.

As can be seen in figure 1, the electrodes of the proposed ES are hollow. They circulate a cooling agent, for example, air (indicated by curved arrows) from a suitable source of pressure difference. By regulating this flow, the thermal regime of this ES can be optimized.

Due to efficient cooling, the proposed ES can be used with “long" electrodes, which protrude far into the combustion chamber. For example, in the device diagram of the proposed ES (Fig. 1), the spark gap is quite far from the threaded part of the ES, approximately 1.75 of its diameter. With the standard diameter of the threaded part of the electric motors used in piston ICEs of passenger cars, the electrodes according to the given drawing should protrude approximately 22 mm into the lumen of the combustion chamber. That is, several times further than conventional ES. This value is close to half the length of the radius of the combustion chamber of most piston ICEs. Obviously, with such a length of the electrodes, their cooling due to heat transfer to the wall of the combustion chamber is inefficient, the electrodes must overheat and acquire the properties of a glow plug. While air flowing through hollow electrodes (or another cooler) can remove heat very efficiently.

The use of the proposed ES with electrodes “far” protruding into the combustion chamber in reciprocating internal combustion engines can significantly reduce the time of effective combustion of the fuel-air mixture. Indeed, since “long” electrodes make it possible to move the spark gaps (centers of ignition of the combustible mixture) sufficiently far from the wall of the combustion chamber, the distance traveled by the combustion front of the mixture from these gaps to the areas of the combustion chamber most distant from them is noticeably shortened. Consequently, the overall time of the effective, useful work of burning the mixture is also reduced.

This is illustrated in figure 2, 3, 4, which schematically depict:

- the contour of the combustion chamber of the piston internal combustion engine, preserving the proportions of the combustion chamber of the internal combustion engine of a real production car;

- the location of the spark gaps of the proposed ES with electrodes of different lengths and “normal” ES;

- the distances traveled by the combustion fronts from spark gaps to the “most distant” areas of the combustion chamber.

Figure 2 - the position of the spark gap in the combustion chamber and the mean free path of the combustion front when using a "normal" ES.

8 - wall of the combustion chamber; 9 - the working surface of the piston located at bottom dead center; 10 - the position of the working surface of the piston at the time of opening of the exhaust valves; O - spark gap; A is the “most distant” region of the combustion chamber from the spark gap; OA - the maximum distance traveled by the combustion front of the mixture.

Figure 3 - the position of the spark gap and the length of the largest path of the combustion front when using ES with electrodes protruding into the combustion chamber for a length of about 50% of the radius of the cylinder.

8 - wall of the combustion chamber; 9 - the working surface of the piston (with a recess for the electrodes) located at bottom dead center; 10 - the position of the working surface of the piston at the time of opening of the exhaust valves; 11 - ES electrodes protruding into the combustion chamber; O - spark gap; A is the “most distant” region of the combustion chamber from the spark gap; OA - the maximum distance traveled by the combustion front of the mixture.

Figure 4 - the position of the spark gap and the length of the largest path of the combustion front when using ES with electrodes protruding into the combustion chamber for a length close to the value of the radius of the cylinder.

8 - wall of the combustion chamber; 9 - the working surface of the piston (with a recess for ES electrodes) located at the bottom dead center; 10 - the position of the working surface of the piston at the time of opening of the exhaust valves; 11 - ES electrodes protruding into the combustion chamber; 12 is an example of the arrangement of a “long” (approximately 50% of the radius of the combustion chamber) ES along the longitudinal axis of the combustion chamber (for explanations see the text); O - spark gap; A is the “most distant” region of the combustion chamber from the spark gap; OA - the maximum distance traveled by the combustion front of the mixture. The orientation of the longitudinal axis of the ES is the same as in figures 1 and 2.

When using the proposed ES, the working surface of the piston must have an appropriate shape. For example, it can be flat with a relatively small length of the protruding parts of the electrodes of the electrodes protruding into the chamber (Fig. 3). Or, in the case of a large length of the parts of the electrodes of the electrodes protruding into the combustion chamber (which may even exceed the value of the radius of the cylinder), have a special recess where these electrodes are immersed when the piston is raised to its upper position (Fig. 4). That is, at all positions of the piston, the ES electrodes do not touch its surface.

The design of the proposed ES should be such that the electrodes protruding into the combustion chamber of the piston ICE do not interfere with the movement of the valves. A constructive solution to this problem is facilitated by the fact that the electrodes of the ES can be located in the same plane (as in figure 1). Due to this, they are easily placed outside the zone of movement of the valves.

As follows from figure 2, 3, 4, at different positions of the spark gaps, the “remote” areas of the combustion chamber are in different places of the combustion chamber. In Figs. 2 and 3, these regions are located at the edge of the piston working surface opposite to the spark gap at the moment of opening the exhaust valves, and in Fig. 4 - the regions along the entire edge of the piston working surface at the same moment.

This moment, which is equal to angular degrees from the start of the working cycle for the ICE as an example, is selected to determine the maximum path length of the combustion front due to the fact that when the exhaust valves open, the pressure of the hot gases in the combustion chamber drops rapidly and they cease to do useful work . Therefore, the propagation of the combustion front beyond this, called “remote”, area of the combustion chamber becomes impractical. Ideally, the combustion of the mixture at the time of opening the exhaust valves should generally cease.

From a comparison of the lengths of the ranges of the combustion fronts, graphically depicted in figure 2, 3, 4, it follows that:

- if the electrodes of the proposed ES protrude into the chamber to a length of about 50% of the radius of the cylinder, then the range of the combustion front is reduced by 17% compared with the “ordinary” ES;

- if the electrodes protrude into the combustion chamber by a length equal to about 100% of the radius of the cylinder, then the range of the combustion front is already reduced by 37%.

In a first approximation, the time of combustion of the air-fuel mixture decreases by the same values (determined by the maximum time for which the combustion front will cover the distance from the spark gap to the “most distant” region of the combustion chamber). Due to this, the ignition of the mixture in the piston ICE when using the proposed ES can be produced much later than when using the “ordinary” “short” ES.

If in the internal combustion engine selected for calculations when the mixture is ignited, the “normal” ES ignites the effective burning of the mixture (from the moment of ignition to the opening of the exhaust valves) at idle (800 rpm) is equal to 146 angular degrees, then the proposed ES allows ignition later than the usual moment ( in comparison with the “ordinary” ES in figure 2) by approximately the following values:

for figure 3 - 24 degrees;

for figure 4 - 51 degrees.

The above calculations for idling are purely approximate and for a different composition of the mixture and other modes of operation of the internal combustion engine will be different. However, it is obvious that even at fairly high engine speeds, it is possible to ignite the 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.

For the cases in FIGS. 3, 4, the initial pressure increase 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).

When the mixture is ignited simultaneously in two spark gaps of the same ES (see below), the rate of initial increase in pressure in the operating cycle increases compared to the “ordinary” ES even more, approximately 4 times. In one combustion chamber can be used not only one, but also 2 or more of the proposed ES.

The proposed ES opens up a large field for modifications regarding the design of the ES, optimizing the location of the ES itself, the spark gap (spark gaps), and the thermal regime. We emphasize that the design of the proposed ES in principle allows you to arrange spark gaps (ignite the mixture) in various places of the combustion chamber.

The proposed schematic diagram allows us to design ES with two or more independent spark gaps connected with different sources of electric voltage, located at a sufficiently large distance from each other along the longitudinal axis of the ES. For example, it can be an ES with one “grounded” electrode and two active electrodes having different lengths, forming 2 independent spark gaps with a “grounded” electrode. ES with two or more spark gaps will further reduce the burning time of the mixture and the rate of increase in pressure of the burning mixture in the working cycle. The proposed ES can be oriented and mounted in the combustion chamber of the piston ICE in a different way than shown in FIGS. 3 and 4. For example, the “long” ES can be oriented, as shown in FIG. 4 (5), along the longitudinal axis of the piston combustion chamber ICE.

The proposed ES can be applied not only in piston ICEs, but also in other ICEs with electric ignition of a combustible mixture.

Claims (1)

An electric spark plug for internal combustion engines includes a metal casing, electrodes and an insulator separating them, characterized in that its electrodes are hollow and air or another cooler is passed through them for cooling, and the length of the parts of the electrodes from spark gaps to the wall of the combustion chamber is more than 10% of the radius of the cylinder.

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