US2250364A - Engine and method of fueling the same - Google Patents

Description

July' 22, 1941 M. G. FlEDLl-:R 2,250,364y

ENGZIINE` AND METHOD OF FUELING THE SME Original Filed July 3l, 1955 3 Sheets-Sheet l Fw @xbm/ef ZfZ-a George r July 22, 1941- M. G. FIEDLER I 1 2,250,364

ENGINE ANDMETHOD QF FUELING THEVSAME Original Filed Jul-y 3l, 1935 5 Sheets-Sheet 2 July 22, 1941.

M. G. FIEDLER ENGINE AND METHOD 0E EUELING THE SAME original Filed July 31, 1955 5 sheets-sheet s maar: eoryeffecr i/gi Pfaff Patented `luly 22, 1941 ENGINE AND METHOD OF FUELING THE SAME Max George Fiedler, Chester, Pa., assignor to Fiedler-Sellers Corporation, Philadelphia, Pa., a corporation of Pennsylvania continuation of application serial No. 34,134, July 31, 1935. This application January 31, 193s, serial No. 183,017

3 Claims.

This invention relates to a method of operating compression ignition engines of the oil burning type, or that type usually referred to as Diesel engines, and is a continuation of Igny prior application Serial No. 34,134, filed July 31, 1935. An important object of the invention is to provide a method of operation of such engines whereby they may be made to operate substantially in accordance with what is known as the Otto cycle, and to operate at variable speeds comparable to those of the ordinary gasoline engine employed in automobiles without detonation throughout such speed ranges.

It is well known that the combustion of hydrocarbons may be either a direct oxidation or a decomposition followed by oxidation of the destruction products. In practice, there is `a race between the two processes, the conditions being more favorable to hydroxylation when a fuel has been properly divided and mixed with air before it is burned, at which time the llame is blue and has no tendency to soot. The conditions are more favorable to destructive combustion when the fuel is exposed Very suddenly and in a highly vaporized condition to flame temperatures, the fuel particles decomposing rapidly before they can find oxygen, and under these conditions there is a yellow radiation caused by the burning carbon and a tendency to form soot.

In the ordinary Diesel engine, air is compressed to the greatest possible extent to prevent ignition lag, and a readily ignitable oil is employed for the same reason. I have found that in high speed Diesel engines having a high compression ratio the first fuel entering the combustion space does not ignite but meets with the turbulent compressed air. Part of the entering fuel will mix with more or less turbulent air until, in

some part of the chamber a suitable mixture.

for self-ignition has been established and combustion will start. If the duration of injection is continued after combustion has occurred,A this fuel will meet air which is. not only strongly .turbulent but mixed with combustion residue.

As injection continues, the air becomes saturated With the products of combustion until the interference with further combustion is so serious that free carbon will be generated. In the ordinary Diesel this occurs at a point where approximately 50% of the available air has been consumed. The time necessary to establish the `proper mixture for the rst auto-ignition is equal to the ignition lag and is influenced to a great extent by turbulence during injection, but

also =by the shape of the combustion chamber, the spray characteristics, duration of injection, and, to some extent, by the compression pressure. To a large extent the ignition lag in the engine is directly dependent upon the degree of turbulence, increasing with such turbulence due to the fact that the air usually rotates at high speed around the cylinder axis throwing the entering fuel into the coldest zone adjacent the cylinder wall. This can only be counteracted through high compression and it follows that previous engines having high turbulence must work under very high compression pressures, often asvhigh as 40 to 50 atmospheres, and even under these circumstances detonation frequently results.

Analyzing the standard spray characteristics as produced today in the usual solid fuel injection engines, it is found that the fuel, through being subjected to high injection pressures (3,000 to 20,000l lbs.) and through being forced through very small orifices is substantially in a vapor stage and thus readily subject to cracking In addition to that, as has been photographically demonstrated-the spray itself is very compact and cannot be broken up even by the. most violent turbulence. This spray 1s, therefore, exposed to highA compression temperatures without the ability to mix with air and the result is, inevitably, cracking 'Ihe combustion will, therefore, follow the second type mentioned above and since part of the combustion will be a hydrogenoxygen or oxygen-methane reaction at the high temperatures and pressures existing in Diesel engines, will undoubtedly, be extremely violent and destructive. Furthermore, since the injection is through such ne orifices, the injection period necessarily, and of course purposely under the Diesel system, continues after combustion has actually begun and, obviously, the later injected fuel will crack producing further hydrogen-oxygen reactions.

I have discovered that the proper operation may be provided by observing the following precepts:

1. In small bore, short stroke engines the use of a relatively large combustion space and the maintenance of the air inthis space in a high state of turbulence in `order that the mixture may be as complete and rapid as possible while maintaining the turbulence of such character that there is no localizing disturbance or deformation of the jet.

2. The instantaneous, or substantially instantaneous injection of the fuel into the combustion chamber, and the use of low compression pres- I sures (approximately 240 pounds at the time of starting injection) thereby causing a combustion lag, in order that all of the fuel may be delivered thereto before combustion begins without regard to the speed or load conditions under which the engine is operating.

3. The introduction of the fuel spray into the combustion chamber in the form-of a loosely bonded liquid foam and under relatively low injection pressures (preferably less than 1200 l-bs.) thereby enabling the relatively cool fuel to readily combine with the air in the combustion chamber and establish an auto-ignition mixture as rapidly as possible, and, furthermore, prometing the combustion lag during which establishment of the mixture is assured.

An important object of the invention is the provision of a means foi' super-charging the working cylinder so constructed and arranged that losses from interposition of receivers or recompression of any appreciable volume of air handled by the compressor unit is eliminated.

A further object of the invention is the provision of a solid fuel injection cycle in which the injection period is in all phases of operation of the engine of such duration that'all the fuel has entered the combustion chamber before combustion actually starts.

Obviously, sudden injection of fuel in this manner` is impractical in a quiescent chamber and, accordingly, a further object of the invention is to provide a structure wherein high turbulence is assured, the turbulence being non-directional in character, and which provides this turbulence without the use of any artificial or additive means for producing the same.

Another object of the invention is the injection of fuel in the engine in the manner outlined in the second and third precepts above.

Other objects of my invention are to provide an engine having two cylinders and pistons operatively mounted therein, one of which cylinders is the main working cylinder and the other cylinl der is the supercharging cylinder and utilizing both of the cylinders as compression chambers; to provide a passageway betweenythe working ends of the cylinders controlled by a valve through which the air is forced and retained in the main cylinder during the firing of the fuel mixture; to provide a novel form of valve for These together with various novel features of construction and arrangement of the parts, which will be more fully hereinafter described and claimed, constitute my invention.

Referringto the accompanying drawings,

Fig. 1 is a sectional view through an engine of a type suitable for use in carrying out my novel method;

Fig. 2 is a cycle diagram of Van engine con-I structed in accordance with my invention;

Fig. 3 is an indicator card showing the pressure cycle of the engine;

Fig. 4 is a conventional injection nozzle of the type at present in use;

Fig. 5 is a sectional view through a nozzle modified for use in accordance with my invention;

Fig. 6 is a diagrammatic View illustrating the type of spray produced by the nozzle of Fig. 5;

' Fig. 7 is a sectional view showing a preferred type of nozzle and the pump connection thereto: Fig. 8 is a highly enlarged sectional view 4 through a portion of the nozzle of Fig. 7;

' large combustion space I2 is` provided,

transferring the air from one cylinder to the other, in which valve a small volume of air under pressure is retained when the valve is closed and again released during the next succeeding operation of the pistons, thus providing air under pressure Whichwill assist in building up the pressure in the cylinders when the next compression stroke takes place; to provide a novel form of rotary inlet valve for controlling the admission` of air to the compression cylinder; to provide a novel means for scavenging the main cylinder at the end of the working stroke of the piston; to provide an engine in which the scavenging air is compressed by both of the pistons in the crank casing and controlled by the movements of the piston for transferring the air for scavenging purposes in a novel manner; to provide a novel construction and manner of operating the inlet and transfer valves; and to construct the engine so that any number of cylinders may be combined for operating upon the same crank shaft and to arrange the casing, of which the cylinders form a part, with novel inlet and transfer passages for controlling the inlet air, combustion mixture, and-the scavenging air.

n Figs. 9 and 10 are card diagrams' showing operation of the engine with the ordinary type of injection; and

Figs. 11 and 12 are card diagrams taken under identical conditions with those in Figs. 9 and 10, but with use of the new type of injection and operation.

The first precept of my invention may be conveniently carried out by the engine forming the subject matter of my copending application Serial No. 247,508, filed December 23, 1938, for Internal combustion engine. 'I'he engine therein illustrated is of the type shown in Fig. 1, having main and supercharging cylinders I0 and il, the main cylinder being so constructed that a relatively The supercharging cylinder Il delivers a suilicient amount of air beyond that obtained from-compression in base I3and introduced for scavenging the main cylinder to provide auto-ignition pres- V sures and temperatures in the combustionchamber considerably prior to complete compression of the charge. The scavenging air is delivered from thebase to lcylinder l2 in a manner such that a high degree of non-directional turbulence is obtained in the cylinder. At the same time the maximum pressure attained in the cylinder should, preferably. not exceed 400 to 450 pounds, and under many conditions considerably lower pressures areA feasible and desirable.

The second precept may, obviously, be obtained in a variety of fashions as, for example, by multiplying the number of nozzles employed and thereby increasing the effective injection area so that the period necessary to injection of a predetermined amount of fuel may be reduced to the desired point. I have found that the injection period should not exceed 10 of crank travel, and preferably should be confined to approximately 7 thereof. Since the engine is now to operate as a constant volume engine, all of the fuel being injected before ignition, it is, of course, desirable that this fuel be entered prior to the arrival of the working piston I8 at top dead center, the arrangement being preferably'that illustrated in the cycle diagram forming Fig. 2, in which the injection is illustrated as occurring in advance'of the top dead center, a distance corresponding to the average combustion lag. While the injection period might be delayed beyond the point illustrated, this will, obviously, result in a loss of efficiency, the operation of the engine under such circumstances 'I'he compression pressure of the engine must be kept sufcientlylowto insure a combustion lag enabling complete injection of the charge prior to initial combustion, and must. be sufiiciently rapid to insure against vapor formation. It will be noted that this is directly contrary to Diesel practice in which the production of highly vaporized sprays is sought and in which the compression pressures are carried to the highest possible point in order to avoid ignition lag.

Such an arrangement as that already suggested will result in a highly improved operation of the engine, but to insure complete elimination of detonation, a smooth operation of the engine over a .vide speed range, and an economical fuel injection system, the construction should be restricted lifting surface 8| provided on such valves, with the attainment of injection pressure, the valve is violently thrown upwardly against a stop 82 and there remains throughout the injection period, the minute discharge orifices providing suincient back pressure to maintain it in this position.

I have found that by materially reducing the lifting area of this valve, as at 8Ia in Fig. 5, and increasing the diameter of the discharge openings 80a to an extent such that the pressure beneath the valve is constantly relieved and at the same time providing the valve with a relatively heavy spring of high frequency, the valve will chatter against the seat, or rather upon the liquid passing over this seat, reducing the fuel to a loose foam of liquid particles which is discharged through the openings 80a atv a much reduced pressure and in relatively large particles. The increase of the size of the openings 80a requires a thickening of the wall 83 through whichxthese openings are formed in order that they may properly guide the fuel and insure correct distribution thereof. The fuel then has a spray characteristic typified in Fig. 6, and is in the form of Well spaced, loose liquid particles as compared with the'usual injection practice, which particles may be readily taken up and surrounded by the air in the combustion chamber, with the result that a thorough comingling is obtained insuring proper proportioning of air to fuel at the time the mixture attains the ash point. As indicated above, the openings should bemuch larger than those ordinarily employed, and in an. injector found to give excellent results 6 openings were employed of a diameter of .9 millimeter as compared to 6 openings having .3 millimeter utilized in the usual injection nozzle; in other words, an increase of approximately 900 per cent in injection area.

In general, it maybe stated that the areaofI the openings must exceed the maximum area afforded by the valve seat 84 and the valve 85 during the injection period. It will be obvious that the valve, during the injection period, acts not only as a valve lbut likewise as a flexible orifice, through which the fuel may enter, exercising upon the fuel because of its flexibility an agitating action producing a relatively loose foam. The valve seat itself should be of relatively large diameter in order to obtain large impact relief areas with a minimum lift and the valve spring should be strong enough so that at minimum pressure it will counteract the inertia effect of the valve stem under impact and continually attempt to reseat the valve and thus produce the chattering action on the fuel passing over the seat. To this end, as previously stated, a heavy valve spring having a high frequency is preferable.

While the injection nozzle of Fig. 5 provides a highly improved operation, it was found in practice that this nozzle, -after heating to approximately '700 caused detonation. It was finally determined that the foam formed in advance of the nozzle tip by the chattering of the valve upon its seat tended to vaporize at the nozzle tip with resulting detonation in operation. For this reason, the valve of Fig. 7 was developed. In this valve the lifting area is transferred to the center of the valve, ports 88 communicating with a passage 89 opening through the bottom of the valve and into a chamber 90 at the nozzle tip. The valve seat is divided into two sections 9| and 92 by a groove 93 aligned with the discharge ports 94. By this construction all foaming fuel is discharged from the valve and the tip of the nozzle is kept cool by maintenance of a solid body of the fuel thereagainst.

Tests with an injection nozzle of this type have proven conclusively not only its value in improving the explosion characteristics ofY the engine but likewise that for maximum efficiency certain definite characteristics and proportions should be employed in the injection system exterior to the nozzle. I have found, for example, that the injection at the nozzle is responsive not so much to the injection to the system by a measuring pump of a predetermined amount offluid as to the impact resulting on the fluid line from the initial opening of the fuel line to receive the fuel displaced by the pump. 'Ihis is evidenced by the fact that the injection period does not appreciably vary through a considerable range of injection as regards the amount of fuel which passes through the nozzle. With' the same nozzle it is possible to inject 10 to 100 cubic millimeters of fuel to the cylinder in the same interval. This is apparently due to the fact that with a greater fuel injection a greater residual pressure exists in the lineconnecting the pump and nozzle and,

accordingly, the impact blow resulting on initial injection is transmitted with greater force to the valve. The injection apparently immediately follows the closing Aof the intake openings 86 of the pump by the piston 8l thereof. The speed of operation of the pump piston apparently has little eiect on the injection although it is found that a greater fuel injection can be obtained through use of a relatively slow operation of the piston. In actual use, sharp, medium and eccentric cams have been utilized, and it is found that the eccentric cam gives much the best results, the sharp cam tending to upset equilibrium of the system. The indications are, accordingly, to the use of a large 'diameter pump operated by an eccentric cam through a short plunger travel.

I have, further, found that there are definite characteristics necessary to the discharge line connecting the pump and nozzle if proper injection characteristics are to be obtained. For example, a discharge nozzle having openings of the size above mentioned employed in an engine of the character described must have a discharge line of definite length; in the construction under 4 test, .533 meter. It is found that a' shorter une causes double injection; that is to say, there area long line might be overcome by a reduction of the diameter of the discharge line, but thisis not the case, for it is found that unless the diameter above-outlined circumstances as against the normal injection methods may be visualized by comparing the indicator cards forming Fl'gs. 9 to 12.

' 'Iheindicator cards of Figs, 9 and 10 are cards compact spray in accordance with the principles of the line is kep't quite large the impact blow creates such high speed in the column that it cannot be controlled by the valve or flexible orilice. As a matter of fact, I have found that a relatively large line as compared to the standard line of 0 to 2 millimeters in diameter is essential and in practice employ a line at least 3, and preferably 4 millimeters in diameter. In any case, the line must be large enough to prevent `too great an impact and, in general, the larger the amount of fluid to be injected, the larger the line should be. It has also been found that the amount of fuel injected through a given period can be varied within given limits by variation of the size of the pump employed. For example, a pump having a piston 10 millimeters in diameter provides an injection range between 10 and 100 cubic millimeters, While with the same line and conditions a pump having a piston of 13 millimeters in diameter provides an injection range of between l0 and 160 cubic millimeters in the same injection period.

I have determined that the temperature range at which injection should take place in order to permit the proper ignition lag enabling all of the fuel to be injected before combustion starts is provided by ay compression pressure having a minimum of 120 pounds 'per square inch and a maximum of 400 pounds per square` inch, the most ecient rangebeing between 330 pounds and 360 pounds to the square inch. In this range the temperatures are sufficiently high to cause rapid heating of the material and are at the same time below the decomposition temperature when the fuel is delivered to the cylinder in the form of a coarse spray.

It will be noted that there is again a sharp deviation from the ordinary Diesel practice and this deviation assists in providing the necessary lag enabling the establishment of the auto-ignition mixture with complete injection of the fuel prior to auto-ignition. Due to the fact that low pressures are-employed in injecting the fuel, the fuel itself enters the cylinder at a much lower temperature than is possible when injection takes place under the usual Diesel system. Since the fuel injected is substantially incompressible,

of present-day Diesel practice.

It will be noted that a succession of detonation peaks D appear even when the engine is idling, as in Fig. 9. These peaks are much exaggerated when the engine is-operating under load, as indicated at D in Fig. 10. On the contrary when the type of injection just described is employed in the same engine and under the same conditions, these peaks immediately disappear and when idling or under load the engine shows no tendency to the detonations responsible for these peaks. (See Figs. 11 and 12.)

Through the use of this method of fueling the engine and the nozzle construction hereinbefore described, I am able to produce an engine which is particularly adapted for Iuse in automotive fields. In an engine from which the indicator cards forming Figs. 11 and 12 were taken when using the new fueling system, such engine having 4 cylinders and a bore and stroke of 3:/12 and 4" respectively excluding the exhaust port area, when operating at 1800 revolutions produced 150 H. P., at 1,000 revolutions produced 80 H, P. It is, however, operable in the higher automotive ranges; that is to say, 3,000 to 4,000 revolutions.

It will be noted that an engine operated as above described operates neither on the Diesel nor the Otto cycle, differing from the former in that the fuel injection occurs through an extrerriely short period and entirely prior tocomall work done in injecting the fuel in the cylinder must, be converted to heat in the fuel itself. With the light injection pressure the fuel may enter without in any way approximating decomposition temperatures and may, accordingly, combine with the air to provide a complete auto-ignition mixture before such temperatures are reached. The resultant explosion is. therefore, a soft-burning as differentiatedfrom the detonating characteristics of fuel injected under the usual circumstances.

The vast improvement in operation of an engine operating with fuel injection under the bustion; that the injection employed is a spray of loose particles rather than a highly vaporized injection; that an ignition lag is deliberately sought for, to enable the injection to be made prior to combustion, and that volumetric capacity of the engine is greatly increased from the ordinary Diesel, with the result that much higher engine speed can be obtained. It differs from the Otto cycle both in the fact that the volume of air introduced is materially increased, and that the fuel is separately injected.

Since both the method illustrated and the con-A struction described are capable of considerable modification without departing from the spirit of the invention. I do not wish to be understood as limiting vmyself thereto except as hereinafter claimed.

I claim:

l. The method of operating variable speed solid fuel auto-ignition type internal combustion engines which consists in compressing air in the engine' cylinder to an extent affording auto-ignition temperatures and maintaining said air in a state of turbulence, and instantaneously injecting a complete charge of fuel into the cylinder in the form of a loosely bound mass of liquid partemperature and delivering the fuel to the chamber in a. wet state while maintaining the pressure in the chamber suiciently high to cause combustion and sumciently low to insure an ignition 3. The method of claim 2 wherein the fuel is introduced to the cylinder through relatively large openings and prior to injection is subjected to the action of a. flexible orifice causing the fuel to foam lag preventing combustion of the Wet fuel prior 5 and be divided into loose particles.

to the complete injection of the charge.

MAX GEORGE FIEDLER.

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