Process allowing the combustion of weak mixtures in the engines with positive ignition.

AS AFRICAN AND MALAGASY

EO INDUSTRIAL PROPERTY

P. 887

Yaounde (Cameroon) Patent International Patent Classification: 02 no. 01620 F.

ΟΛ№Ρ, 1

31 December 1964 to 18 hr 36 requested Mn to the O.A.M.P. I-.

(G.P. no. 51,702) by french petroleum Institute, fuels and lubricants, residing in France.

Delivered 20 September 1969, published at Official ballot no. 3 of 1969. Priority: Patent application filed in France under the n° G.P. 800,854 21 July 1959 on behalf of the requester.

Method for the combustion of lean mixtures in spark-ignited engines. (Disclosure: BAUDRY jeans.)

The present invention, due to the work of M. LOA -

dry fluxing, concerns a novel supply method

of spark ignition engines for the func -

how does thereof by combustion of mixtures

carburetted lean, it is to say - fuel mixtures

oxidizer in which the proportion of fuel

is lower than that of a stoichiometric mixture

(richness equal to unity), corresponding, when the

oxidant is air and the fuel of gasoline, to

about 15 g of air for one gram of gasoline, these

ratios varying somewhat with the nature of the

fuel.

The use of lean mixtures for the combus -

except in combustion engines present by RAP -

port to employing mixtures rich many Bene -

compensation-whose main are:

1° fuel economy whose consumed -

translocation is reduced by enhancing the efficiency

thermodynamic efficiency is improved by and

combustion. Rich do not burn that MI -

perfectly and the products of its combustion - NER

close still unburned combustible gasses. The

thermal efficiency of combustion is far into

these conditions being optimal.

This results in significant reduction in 2° proportions of

toxic elements of the exhaust gas and, in advantage -

evicriminal, carbon monoxide.

3° reduced deposits of scale - ments provided

wetted the combustion chambers of the engine, deposits

due, in a large amount, to the wrong combus -

except charbonnement generator.

The combustion of lean mixtures is easily

carried out in the compression ignition engines

it is only necessary to vary the amount of combusti -

wheat injected by adjusting the feed injectors

appropriately.

Indeed, inflammation of the load results from the

compression of the mixture produced after injection of

fuel and inflammation which occurs always

in delays shorter or longer periods after injection

for injection quantities which may range from full

load to a very small fraction thereof accounted -

matches the idling.

On the contrary, in a petrol engine has,

inflammation of the fuel-air mixture can be made not in good conditions by the means currently employed if the richness of the mixture is less than about 0.9, it is to say if the proportion of fuel in the air-fuel mixture is lower than 9/10 " of the stoichiometric amount.

Indeed, in such an engine employing a fuel mixture of a richness equal to or less than 0.9 causes unevenness of igniting the mixture of a cycle on the other.

This results in instability of engine operation and a significant increase of the specific consumption thereof attributable to a significant reduction in the rate of combustion.

Such a result is against the goal pursued by the supply of lean operation including a decrease in the specific consumption resulting in saving fuel.

Indeed, when not request engine that reduced power, and especially when operated at idle, required to reduce correspondingly the amount of fuel used. But, if this is possible, in the case of a separate injection of fuel into the oxidizer (compression ignition engines) without reducing the filling air admitted, it is not even in the case of a power supply by external carburation because the phenomenon of inflammation occurs then under conditions suitable for a richness that minima of the mixture. The only means to reduce the flow rate of fuel at reduced power then reduce in conjunction by the filling of the engine air-fuel mixture, the richness of the mixture generally to be in this case greater than unity.

The present invention is precisely to be solved by supplying lean burn engines external carburation under conditions such that the smoothness of engine operation is at least as good as in the case of power using a fuel mixture rich (richness of the order of 1.1) and that the combustion is improved, thereby implementing as completely as possible the advantages of a reduction in the specific consumption resulting therefrom.

Various solutions have been advocated for improving conditions for the combustion, and might be applied to enable operation of a spark ignition engine with a lean mixture supply.

Solutions employ the following means:

1° increase the turbulence of the mixture.

2 An increase in energy which serves to ignite the charge of fuel-air mixture.

3° embodiment a mixture of heterogeneous richness by the use of an injection device.

The first of these means allowing only a small decrease in the richness of operation possible and has the disadvantage of reducing the coefficient of filling of the engine thereby advancing tradnit essentially impossible to use the engine to its full initial power.

The second means is generally implemented by performing a hardware partition of the combustion space into two parts, formed for example by two separate combustion chambers and communicating (combustion space having a prechamber) or by two separate areas of the same combustion chamber, defined for example by a wall.

According to this type of device, one of the parts of the combustion space, hereinafter primary chamber, is supplied with mixture ratio above the overall richness and includes the spark plug while the other called the "secondary chamber" by is powered only lean or possibly air. The power supply of each of these portions of the combustion space can be performed separately using different valves, which is the case in the so-called pre-chamber engines, or by means of a same valve using deflection means for distributing the flow of different wealth.

It is possible, by this method, to obtain a proper combustion of a mixture generally lean, by maintaining a richer mixture in the primary chamber, the energy released by the combustion therein enabling a combustion sufficiently fast from the remainder of the charge of fuel-air mixture.

Such devices supply have been - described for example in patents Americans N.^bone 1.483.619, 2.121.920 and 2.196.860. If their use is well capable of allowing the combustion of lean mixtures in spark-ignited engines, it has however of major drawbacks due to which the adaptation of such devices to automotive engines ignited only gave rise to any industrial development.

These disadvantages are essentially the following:

1° separating the combustion space in a primary chamber and a secondary chamber, leads to a decrease in the thermodynamic efficiency offset the gain in efficiency resulting from the use of a lean mixture. This decrease in efficiency results, on the one hand, because the ratio of the volume to the surface of these two combustion chambers is always lower than the corresponding ratio for a single combustion chamber and that, therefore, the heat loss through the walls is greater thus tending to lower the thermodynamic efficiency, all things equal also. U is due also, on the other hand, to the energy loss resulting from the need for transfer of combustion gas from the primary chamber to the secondary chamber.

2 The separation into two parts of the combustion space requires the use of a special cylinder head or even, in some cases, a particular engine because of the necessity of bringing œuvreœuvre.une additional valve (motor case to prechamber). This prevents the application of the device for ambulation lean engines already existing, current type.

3° if return walking into a rich, taken to achieve full power, loss of thermodynamic efficiency remains and results in not only an increased consumption but also by a lower performance maximums.

The third means of using an injection device for producing a mixture of heterogeneous richness can be combined or not with the use of a primary chamber. The injector can be disposed either in the primary chamber, either in the single combustion chamber, either in the intake duct upstream of the intake valve. In any case, the result is an increase in the mechanical complexity of the engine and its cost price. In addition, the realization of this means provides the problems incorrectly resolved petrol injection and, in particular, that of the dosing a small amount of liquid fuel in accordance with the intake air flow rate.

The present invention can benefit from the numerous advantages in using lean mixtures (more complete combustion resulting in a significant reduction in the proportion of unburned gas and the carbon monoxide concentration of exhaust gas, as well as by reducing fuel consumptions correlative) without the disadvantages mentioned above and, in particular, without the need to construct new power engines.

The method of the present invention may, indeed, be applied without difficulty to the engines of known type having a chamber homogeneous combustion, it is to say a chamber as evenly as possible, thereby excluding the motors whose combustion space is constituted by two separate combustion chambers and connecting surface or by two distinct zones of a same chamber, defined for example by a wall. The hemispherical chambers respond well to this homogeneity condition still so that advance chambers whose shape deviates some PEN thereto, provided are homogeneous.

The method consists in the combustion chamber a heterogeneous mixture of different local wealth as the mixing section and the richer in fuel is provided near the spark plug. This heterogeneity is achieved according to the invention without division hardware of the combustion space and additional valve or injector without the use of just upstream of the intake valve S_has (figure 1 exemplary non-limiting) of each cylinder of the engine a double supply of fuel-air mixture in variable proportions by two distinct conduits containing themselves mixtures of different richness, the leaner could even be consisting of clean air. By directing the intake duct containing the mixture the richer grams_{the R} toward the region of the b-hougie ignition, it has been found experimentally that it was possible to maintain ignition until adequate local abundance ratio around the spark plug for initiating in good conditions the combustion of mixtures whose overall richness is less than 0.9 and particularly lean overall richness of the order of 0.5.

These are a result quite surprising and unexpected in light of the knowledge acquired to date in this field. Indeed, all would provide suggests, on the contrary, that the simultaneous suction by opening the valve of the two mixtures of different richness during downstroke of the piston, followed by their progressive compression throughout the rise of the piston, would realize some stirring two mixtures tending toward a homogenizing the mixture overall, this would at substantially the same result as into standard lean. It is certainly the reason for separating the space into two parts has been advocated to date since it performs a substantial separation of the mixtures of different richness carburetted.

On the other hand, the idea of performing a heterogeneous mixture from two mixtures of different richness carburetted considering any revolutionary appears prior teachings as one of their objectives was specifically seeking the most perfect homogenization can be carburetted mixtures into the combustion chamber, this homogenization being considered one of the best means for improving the efficiency of combustion.

The present invention demonstrates, on the contrary, that a more complete combustion and more perfect mixture generally lean, rich lower average for example 0.9, is obtainable in a petrol engine has by performing a heterogeneity sufficient area attraction of this mixture. The heterogeneous mixture can be obtained according to the invention from the two intake ducts C._{the P} and c_{the R} (figure 1) located upstream of each valve, each fed by different wealth carburetted mixtures, blends the richness of a past at least enough to cause inflammation of the mixture by the spark plug in good condition is? (richness of at least 1.0) and can be as high as desired and the richness of the other mixture can be chosen at will between zero richness (corresponding to pure air) and richness of 1.0 to suit the desired overall richness for idling operation of the engine, given the respective proportions of mixtures admitted into each of the intake pipes.

Experience has shown that the overall richness minimum allowable to permit stable operation of the engine and a proper combustion was achieved in the case of a heterogeneity maximums area attraction, corresponding to the introduction of all of the fuel as a mixture very rich (richness of at least 5 and preferably between 20 and 50) by the special conduit intake C._{the R} directed towards the region where the candle while the conduit during normal intake C._{the P} only intakes air.

The richness of the air-fuel mixture with the highest may be as large as desired, although in most cases should not exceed a richness of the order of 100 to be able to sufficiently precise metering of small quantities of fuel without the need for high-precision devices such as injectors for example.

These conditions for implementing the method according to the invention enabled for example operating a petrol engine has using a mixture of an average of 0.5. Of course, the allowable minimum average richness for proper operation of the engine will depend in each particular case of the shape of the combustion chamber and particularly the relative arrangement of the inlet valve e_has with respect to the spark plug b in the engine under consideration.

Figures 1, 2 and 2a show two examples of adaptation of the device according to the invention, Figure 1 on an engine cylinder to cylinder head hemispherical, Figures 2 and 2a on the 4 cylinders of an automobile engine with overhead valve arranged in a line.

In both cases, the special conduit for g mixes the richer has its terminal end oriented towards the spark plug b., and extended as close as possible the tulip of the intake valve S._has . This special conduit is in these examples disposed inside the intake duct normally C_{the P} but any other arrangement may also be adopted, provided that said duct opens upstream of the single inlet valve.

The use of lean mixtures results in a decrease in power maximums, this use cannot be permanent in the case of engines for which this power maximums may, at times, be requested to the motor, which is the case of the car engine. II is then necessary to be able to vary the overall richness of the mixture according to power demand of the motor. In particular, it is necessary to be able to operate it at a richness corresponding to the maximum power for a predetermined regime (value of R close to 1.10). The use of lean mixtures must be then reserved to the conditions of use for which only a fraction of its maximum power (full load) is requested to the engine at a determined speed.

According to the method of the invention, it is possible to vary the average speed of the mixture continuously and instantaneously, the value corresponding to a minimum ensuring proper operation of the engine (the R close to 0.5), up to the value for the maximum power (the R close to 1.10). This could be achieved gradually increase the flow rate of rich mixture, the air intake of the engine remains substantially constant for a predetermined regime. As grown and the mean richness, it has been found experimentally, that it is necessary to prevent the blending locally over-rich in the vicinity of the spark plug, gradually reduce the heterogeneity of the mixture. This can be obtained in particular by deriving an increasing portion of the rich mixture in the intake air (introduced by the conduit during normal) as the desired increase the overall richness. This method provides for a richness close to the mean richness at the maximum power, a heterogeneous mixture, as is done in conventional carburizing.

For each fraction of desired load the ratio:

amount of rich mixture fed through the conduit special

amount of rich mixture diluted in air intake

is susceptible to variations in so wide around the optimum ratio, without substantially affecting the efficiency of the engine. This optimum ratio decreases with increasing overall richness needed to achieve the desired load increase. In other words, the heterogeneity of the mixture must be all the greater the overall richness is lower. The richness overall minimum usable corresponds exactly to the heterogeneity maximums can be implemented by the method of the invention.

The possibility for continuous variation of the overall richness adjusts the engine load only by variation in richness between full load and the portion of the charge corresponding to the minimum of the richness usable (i.e. for example in the case of the engine described below, about 50% of the full load to 2,000 revolutions/miuute for r=0.5), the engine remains constantly at full inlet (coefficient of maximum filling). This method of varying load is similar to that used on most industrial diesel engines for which the load is controlled only by varying richness, itself designed by varying the fuel flow, the air filling in remaining constant.

Between 0 and 50 % a full load, the quantity of fuel admitted must be adjusted by varying the filling factor, change obtained by throttling the intake. For this area of use, the mean richness is constantly maintained at a value substantially fixed and near the minimum usable richness, which, in view of the variation of the coefficient, results in a proportional decrease in respective flow rates rich and intake air.

Performing the rich fuel-air mixture can be achieved by either a carburetor specially adjusted, or by any other means. Figure 3 shows a non-limiting example embodiment of the method with use of a single carburetor in c.

The flap has serves to control the flow of rich mixture in the special conduit C._{the R} , the vane B serves to adjust the intake air flow rate in the duct normally C_{the P} .

These two flaps can be conjugated to achieve ratios of passage section constantly homothetic to perform richness constant in the operation region of the engine where the load is controlled by varying the inlet. The lid D controls the flow of rich mixture diluted in the air intake. The opening of this flap controls the enrichment of the mixture taken for the operation area of the engine requiring wealth greater than those corresponding to the tread region volume varying admitted. The opening of the flap D does to begin after the complete opening of the flaps a and b the opening of 3 flaps can be easily performed by a single control.

The method according to the invention is more particularly applicable to-valve engines called "overhead", it is to say those in which the valves are controlled by their upper part, generally by means of rocker arms, and carry their heads in their lower part, these valves may be substantially vertical or inclined relative to the vertical. Further, among these engines, those whose combustion chamber is substantially hemispherical and more generally those whose combustion chamber creates low turbulence of the two feed streams, appear more particularly adapted to take advantage of the maximum advantages provided by the inventive method.

As an example of implementation of the method of the present invention, tests were made on an experimental French described per mm. In the Kermarrec dirty and b. From through mechanical, march 1951.

The single cylinder engine of 80 mm 100 mm bore and stroke, comprising a cylinder head hemispherical and distribution by overhead camshaft, is connected to a dynamo for measuring brake power supplied by the engine. The compression ratio is chosen equal to 7 and the rotational speed equal to 3,000/T-per minute.

The fuel used is a gasoline "tourism" octane number (and data output) equal to 82.

Subsequent runs have been carried out:

- I Search specific consumption minima as conventional carburizing.

In a first series of tests, it was determined, for different loads, the minimum specific consumption of the engine, expressed in grams per horsepower per hour, the supply being effected by means of a single fuel-air mixture of gasoline and air which is varied systematically throughput and the richness acting as the throttle diameter of the nozzle. It is found that the values of the richness of the fuel-air mixture for the specific consumption minima for each of the engine loads are between 0.85 and 0.95 when the engine load is between 40 and 80 % the load maximums, these values rising then until reaching 1 to the load maxima of the engine.

11 is suitable however to note that the specific consumption minima as single carburizing thus recorded do not present a practical interest for the following reasons:

has. Each corresponds to selecting different nozzle, are thus purely theoretical, none carburetor known being able only to provide at will all blends ensuring the specific consumption minimums to different loads and engine speeds.

b.. The engine is running is very unstable and the least operating conditions change causes misfiring and, therefore, a rapid rise of consumption and even the engine completely stops.

c.. The combustion of the fuel-air mixture then being very slow, combustion is not terminated when the exhaust valve opens, even when the ignition timing, resulting in quickly

the deterioration of the valve.

Also the carburetors on conventional engines are first-all adjusted to provide a mixture

richness sufficient to insure proper operation at all speeds and for all loads

the minimum of richness that satisfies said conditions being generally about unit.

In a second test series, corresponding to conditions of conventional carburizing, or thus has powered the motor previously described by means of a fuel mixture of richness equal to 1 and determined.

for each of the engine loads, the corresponding specific consumption.

III. - Search specific consumption in carburizing according to the invention.

In a third test series were fed the same motor using the devices in the Figures 1 and 3 of the present application. The richness of the rich mixture has been chosen equal to 30 for all loads, the fluid lean being constituted by air pure for loads equal to or less than 50% of the load maxima and carburized by air of increasing richness when the load ever of 51 to 100 %. Adjusting the performance was obtained by acting simultaneously on the throttles a and b of Figure 3 for loads less than 50%, whereas, for the higher load ranges, the adjustment was obtained by acting on the throttle'd, the throttles a and b being maintained at their maximum opening position.

The results obtained are indicated in Table I.

The II results from the table above that for all loads lower than the maximum load, the specific consumption resulting from operation of the motor according to the method of the present invention is always lower not only to the specific consumption practice motor (richness equal to 1) but even to

its theoretical minimum.

Similar results have been obtained in other regimes, e.g. to 2,000/T-min (minimum richness: 0.5) and 4,000/T-min (minimum richness:

0.62) and with other compression ratio.

The method according to the invention may both be

out with multicylinder engines. He and a dual cylinder engine "a Panhard Dyna"

an air-cooled type "FLATS Twin", of a capacity of 850 cm³ , here reported a specific consumption to half load of 195 grams/chch.h, 220 grams/ch.h against for the same engine equipped carburetor ORI -

parental opinion actually.

Further, the following additional advantages have

been observed in favor of the method according to the invention.

has. The carbon monoxide concentration of exhaust gas is very low, and it spring of the Table II giving the contents recorded during tests summarized in Table I.

Idle (overall richness: 0.65), the carbon monoxide concentration of engine exhaust gas is established

to 0,008 % according to the invention against 2 to 6% in carburizing according the normal idle speed control.

Table II

b.. The exhaust gas temperature, conditioning the performance of the exhaust valves, which is generally shown as or less than that observed in normal (richness 1) carburizing, as indicated Table III collating the determinations made during tests summarized by Table I.

Thus it has already been indicated, the invention would not be limited by any of the characteristics previously indicated as examples. Thus noting -