US3124112A - Internal combustion engines - Google Patents

Description

March 10, 1964 s. SCHREIBER 3,124,112

INTERNAL COMBUSTION ENGINES Filed April 5, 1961 wee/04mm 0/1. OUTLl-T- 7'0 .s'uMP L use/c4 r/ma 5- 0// INPUT OB/F/C'E United States Patent 3,124,112 WTERNAL CGMEUSTION ENGINES Gus Schreiher, 3%93 NW. Highway, Dallas, Tex. Filed Apr. 5, 1961, Ser. No. 31,018 1 Claim. (Cl. Hit-43) My invention consists of the operational and commercially advantageous application of a high capacity accessory piston air pressure accumulator to each cylinder of any internal combustion. This accumulator is applied in such a fashion that there is an open and adequate communication between the accumulator and the clearance space, the crown of the accumulator accessory piston forming one wall or part of the wall of the combustion chamber. As the result of the yielding of this wall of the combustion chamber by the pressures of combustion, the combustion chamber has a variable volume, consisting of the clearance volume and the displacement produced by the outward movement of this accessory piston from the clearance space. In this instance high capacity indicates the ability of this accumulator to permit the yielding of this accessory piston without marked increase in the force of resistance until the desired maximal displacement of the accessory piston occurs. However, the reduction of such a capacity which might produce a more rapid resistance to the outward movement of this accessory piston might be desired by some manufacturer without any new inventiveness being necessitated. Because of this yielding ability, the accessory piston oscillates with each combustion, depending upon the charge, its outward movement being limited to a desired maximal displacement by a dashpot and its inward movement likewise being limited by a dashpot.

The maximal displacement of the accessory piston should not exceed the displacement of the reciprocating piston at the time of the opening of the exhaust valve. Data presented later are based upon the displacement of the reciprocating piston being identical with the displacement of the accessory piston.

The purpose of applying an accumulator to the combustion chamber is to permit low pressure low temperature combustion and to later recover the energy from the accumulator as pressure on the crown of the reciprocating piston during its power stroke. It is generally recognized and admitted by this inventor that accumulators are basically inefiicient-that is because they do not return all of the energy which they receive due to the loss of heat, friction of rings, etc. It is probably for this reason that such a mechanism as presented here has not previously been utilized-because it has been considered that nothing would be gained by such a device. However, the device is useful because, by prolonging the application of the pressures of combustion to the crown of the reciprocating piston as it descends during the power stroke, the prolonged application of this force on the connecting rod produces an advantageous increase in torque on the crankshaft. By detailed analysis, as outlined later, such an accumulator engine will (if compared to a conventional constant volume engine with a compression ratio of 8, with an onset pressure of 14 p.s.i.a., and with an identical clearance volume) produce an increase in net crankshaft torque output of 16%, presuming the accumulator engine compressed air pressure to be equal to the peak compression pressure.

It is obvious therefore, that such a minor increase might not only be false, the losses of the accumulator and the cost of space and production would not warrant its use except as a research instrument to produce data. Because the proper use of this mechanism will produce very advantageous results, both in increased power from a full charge of fuel, and also increased economy of operation 3,l2d,ll2 Patented Mar. 1@, 1564 with diminished onset pressure I shall produce evidence of the why and how an accumulator combustion chamber should be used to produce such results. I shall later detail the specifications of my new mechanism which makes the how perfectly operational, but which requires the use of a previous invention of mine entitled: Semi-Constant Clearance Volume Internal Combustion Engine. This invention maintains a constant compression pressure despite variation of onset pressures-a necessity in such a case for the peak performance of this new mechanism in instances where onset pressures vary. Such a variation does not occur in the ordinary usage of compression ignition engines.

This new mechanism to be presented here permits (and its high indicated thermal eificiency depends upon) a new type of explosive combustion of as near Zero time as it is possible to produce. Such a combustion requires the use of previously forbidden compression pressures with the production of secondary advantages of great significance. An accu nulator combustion chamber accomplishes thereby three major purposes:

(1) A near zero-time combustion produced at top dead center with tremendous reduction in rejected heat both because of the shortness of time of this great temperature differential between the flame and the cold wall and be cause the temperature of the flame itself will be lower and with reduced dissociation because of the simultaneous expansion of the flaming gases.

(2) The utilization of very high compression pressures, the vast majority of which pressure is produced in the terminal degrees of crankshaft rotation when the curve of pressure increase is almost vertical in its ascent.

(3) The later recovery of this energy when the crankshaft tangential forces are such as to mechanically produce hi h significant beneficial effects on net crankshaft torques.

Although textbooks of thermodynamics contribute much space to the discussion of a theoretical constant pressure combustion (during which work is produced) these discussions do not consider the effect of markedly reducing combustion time. It has long been recognized that the shorter the time of injection and the shorter the time of combustion the greater is the indicated thermal efficiency of compression ignition engines. Dr. Diesel must have been cognizant of the great increase in the positive work loop area of cylinder pressures produced by maintaining the height of the compression pressure throughout the power stroke and that the higher the compression pressure the greater the area. He was also no doubt aware of the reduced shock to the engine resulting from such a pressure curve. However, the only method of producing such a loop during the power stroke in a fixed volume engine is a prolonged combustion with tremendous increase in rejected heat.

Although present combustion in spark ignition engines is of much shorter duration (and for equivalent compression ratios have a much higher indicated thermal ethciency) than that of compression ignition engines, it still is of finite time and spreads as a photographable flame front from the spark plug to the combustion chamber walls. A. R. Rogowski, on pages and 101 in Elements of Internal Combustion Engines, published by McGraw- Hill Book (30., inc, New York, 1953, repeatedly states that detonation consists of the Zero-time combustion of the small portion of the remaining unburned charge when the pressure of this unburned charge reaches the region of 800 psi. In addition, he repeatedly states that pressures of two or three thousand pounds are developed during these detonating explosions and has a diagram of an engine which develops 2800 psi. pressure as the result of the detonation of the small remaining unburned charge. He diagrams this same engine as developing some 800 pounds pressure in its normal combustion. Since combustion pressure in conventional engines is 4.25 times that of compression pressure, I conclude that by the spontaneous short time combustion of a small portion of charge that the pressure within this diagramrned engine represented a magnification of the compression pressure some fifteen times. Tenets of physics would indicate that at approximately constant pressure this same terminal explosion would increase volume approximately 15 times if pressure at constant volume is magnified 15 times.

Some authors state that a detonation combustion is a different type of combustion and chemical reaction because a different colored flame is produced. It is much more likely that this different color produced by a detonation combustion is the result of light emission from electron excitation of the metals of the combustion chamber walls, the result of the high temperature produced by the detonation.

If the chemistry of combustion is not different and an increase in molecules is no greater than normal (6%), how can such pressures and temperatures be produced? The simple answer is that the temperature is elevated because of the shortened time of combustion reducing the loss of heat from the flames to the comparatively cold combustion chamber walls.

Arthur P. Fraas, on page 93, in Combustion Engine, published by McGraw-Hill Book Company, Inc., of New York, 1948, states regarding detonation: the energy of combustion in the last part of the charge is released at a rate as much as a hundred times greater than that for normal combustion. The resulting abrupt and violent increase in pressure produces an audible knock. To paraphrase this author and authority, a detonation type of combsution occurs in about V the time of normal combustion. I am forced to conclude that during such a near zero-time combustion only A the amount of heat is lost to the combustion chamber walls, this source of lost heat being a major source of rejected heat in presently designed engines. The purpose of this discussion has been to show that it is very conservative to expect a fifteen-time expansion of the compression volume during such a type of near-instantaneous combustion.

The temperature and pressure of spontaneous combustion of fuels of various octane ratings apparently is information which is unavailable. It must be remembered therefore that detonation in gasoline engines is the result of the pressures and temperatures produced by combustion, not directly by compression. Rogowski, previously referred to, states that this occurs in the engine referred to at 800 p.s.i. This indicates that when I use a figure of 493 p.s.i. compression pressure, as a means of calculating the effects of this mechanism, such a figure is probably a conservative one to use if a spontaneous combustion inducing temperature is to be obtained or approximated. This compression pressure of 493 p.s.i.a is developed with on onset pressure of 14 p.s.i.a. with a compression ratio of 14 if the compression ratio exponent is 1.35. The calculations to be reported later are based upon such a compression pressure with an expansion factor of 15 times, both considered very conservative estimates. The use of a compression ratio of 14 with an expansion factor of 15 serves to displace the accessory piston of the accumulator to a volume which is identical with the displacement of the reciprocating piston, thereby applying the pressure of the height of compression to the crown of the reciprocating piston throughout its power stroke. It is the purpose of this mechanism in spark ignition engines to elevate the pressure of the mixed gases almost to that of auto ignition, then utilizing the heat of the spark to produce an action similar to that of a detonating cap to a charge of dynamite.

By such an expansion of the peak compression pressure through the power stroke, because of the character of the tangential forces the net crankshaft torque is remarkably increased. The graph of such a net crankshaft torque produces a smooth ascending and descending curve inducive of either tremendous smoothness or the possibility of reducing the number of cylinders necessary for smoothness comparable to that of conventional engines.

In the chapter, Engine Dynamics of the book, The Diesel Engines, Its Theory, Basic Design and Economics, by L. V. Armstrong and .l. B. Hartman, published by the MacMillan Co., N.Y., 1959, these authors present formulae for calculating the position of a piston at any degree of crankshaft rotation and supply tables listing the value of crankshaft tangential forces for each 15 of crankshaft rotation. To see what effect a combination of these three major advantages of this mechanism might produce 1 have calculated the compression ratio, pressure, tangential force of compression and power strokes, etc., at each 15 stage of rotation of compression with an exponent of 1.35 for the compression ratio, and of the power stroke with an exponent of the expansion ratio of 1.3 in a conventional engine with an onset pressure of 14 p.s.i.a. and with a compression ratio of 8, and again with an onset pressure of 4 p.s.i.a. I have also done the same calculations with an engine utilizing an accumulator combustion chamber with an accumulator pressure of 493 p.s.i.a. and a compression ratio of 14 with an onset pressure of 14 p.s.i.a., and again with the same accumulator pressure of 493 p.s.ia. and a compression pressure of 493 p.s.i.a. obtained from an onset pressure of 4 p.s.i.a (by means of a constant compression pressure device) with a compression ratio of 29.8. In both these latter cases an expansion factor of 15 was applied and the surprising mechanical advantages are well illustrated in this expansion. With an onset pressure of 14 p.s.i.a. the full displacement of the accumulator is utilized and the compression pressure height is applied over the full extent f the power stroke. With an onset pressure of only 4 p.s.i.a., the accumulator displacement is utilized thereby applying that same compression pressure height to the crown of the reciproeating piston for 50% of its stroke at which point the crankshaft has been rotated beyond the stage of the highest tangential forces.

Graphs of the net crankshaft torque were plotted for each of these 15 stages of crankshaft rotation. Planimeter measurements of these loops showed that at full throttle (14 p.s.i.a. onset pressure) this new device forced an increase in this area of 166% in net crankshaft torque as compared with the conventional engine. Likewise with the onset pressure of 4 p.s.i.a, this new engine showed an increase of such net crankshaft torque of 731%! It must be remembered that both the expansion factor of 15 and the compression pressure of 493 p.s.i. are probably both very conservative. Should this expansion occur and then a pressure rise ensue after full displacement has occurred in the accumulator, the net torque area would increase almost in proportion to that increase in pressure.

The usefulness of this mechanism in compression ignition engines has been impossible to graph or calculate. However, by the use of multiple nozzles, fog injection, or a return to compressed air injection of the fuel, the injection and the combustion time can be remarkably shortened in such engines without the forbidding Diesel Knock ensuing. This permits and encourages even higher compression pressures in such engines, permitting the use of fuels of lower cetane number than formerly and encouraging a shorter delay time. The other advantages which were noted in spark ignition. engines of a high compression pressure, the later recovery of the energy with the advantageous crankshaft tangential factors, etc. are similarly applicable to compression ignition engines.

Apparently no similar previous concepts or art exist and I profess that this accumulator combustion chamber, the new concepts of combustion which have been presented, and the applications of such a combustion chamber are new. I shall now detail the specifications of such an accumulator combustion chamber to illustrate that the how of this mechanism is both operational and simple. Many other variations of design, position, volume of displacement, etc. are possible, requiring only engineering know how, not inventiveness.

In FIGURE 1, the accumulator cylinder 3 is placed in tne cylinder head, but might well be placed parallel to the block cylinder 7 with a common wall as long as an adequate opening exists between the two cylinders which permits of a minimal clearance volume. The reciprocating piston 8 is shown within its cylinder 7. The oscillating piston 2 of this accumulator cylinder is presented in quarter section with a thin lubrication space 1 between the two sets of rings. The rings most distal from the combustion chamber serve to seal the accumulator and to separate the compressed air from the lubricating oil. The rings nearest the combustion chamber seal that chamber and separate the combustion gases from the lubricating oil. Any blow-by from either chamber therefore is either dissolved in the lubricating oil or is suspended in it and carried to the oil pan for ventilation to the atmosphere.

The lubricating oil enters through a small orifice in the threaded receptacle 4 for the connection of the low presure lubrication system of the engine: It exits through the open orifice of the threaded receptacle for connection of drains to the oil pan. By such orifice control no measurable pressure exists within this lubrication space 1 preventing any excess leakage of oil into either the combustion chamber or the accumulator. It is likewise evident that it is an impossibility for blow-by from either chamber to enter the other because of this flow of oil between the two sets of rings. The volume of this lubricating oil containing space is made a minimum to reduce the inertia of the weight of the oil to a minimum, since the oil in this space also oscillates with the piston. The oscillating piston 2 is also designed to be as light as possible. This is facilitated by having the end opposite the crown open. This open end also permits some of the rejected heat of the piston crown to replace the heat lost from the accumulator system. It is possible to extend the piston crown into the center of this piston 2 with a large surface area to induce the entrance of more heat into the accumulator in some instances.

The piston 2 is also made lighter by cutouts 9 which also serve as air passages. The opening 17 is a threaded receptacle for connection to other similar cylinders and/ or to a hot compressed air tank. Not illustrated is that all of this accumulator system and its connections should be efliciently insulated to maintain heat within this accumulater-except around the water jackets which cool the combustion chamber and rings.

The flange 13 constitutes the part of the piston 2 which enters both the outer dash pot and the inner dash pot formed within the cylinder 15. 'On the return of the piston toward the combustion chamber the inner dash pot is for-med by the piston wall itself above the opening 9 and the wall of cylinder 15. The outer dash pot is formed by the piston flange 1.3 entering the closed space formed by the capped end of cylinder 15 and the Wall of cylinder 15.

A special dash pot construction is illustrated which supplies a check-valve action without allowing any compressible air space outside of the actual dash pot. These dash pots are so located that no increased air pressure is thrown upon the rings of piston 2. This check-valve action permits an instantaneous release of the flange 13 in either direction so that no vacuum drag is placed upon the piston 2 in its rapid bidirectional acceleration. The back wall of each dash pot consists of a diaphragm or washer it) which is cast with integral rectangular hooks at intervals. The cap of cylinder 15 is presented in cut away to illustrate one of these springs 11 which are bolted into place with bolts 14 and are so shaped that the washer with its hooks may be rotated onto these springs and then maintain their position on them. These springs, such as illustrated 11, function to return the washer 10 to the recess of the dash pot after allowing easy withdrawal of the flange 13. There is enough resistance to the return of this washer 1t} afforded by the passage of air through its own restraining wall that noise is minimum. Air passages 18 are designed to permit this check-valve action of each dashpot. In the case of the near dashpot of FIGURE 1 the 'back wall is not completely formed by this washer, the cylinder 3 wall forms the portion 16 next to the oscillating piston 2 to prevent adherence of this washer to the wall of the oscillating piston.

By stopping the outward motion of piston 2 with dashpots at the particular displacement desired, no further increase in volume occurs and the pressure then increases in the combustion space because the crown of piston 2 is prevented from further movement, thereby temporarily nullifying the action of the pressure present in the accumulator. However, the pressure of this accumulator is transmitted to the crown through the slits 9 in its side wall and as soon as the pressure in the combustion space is less than the accumulator pressure, the crown of piston 2, because of the free movement of the entire piston 2, will then transmit this accumulator pressure to the gases of the combustion space and thence to the crown of the reciprocating piston, thence as force to the crankshaft. This pressure is applied by the crown of piston 2 to the combustion space until the movement of piston 2 toward the combustion space is stopped by the near dashpot. After this occurs the pressure of the expanding gases is continuously applied to the crown of the reciprocating piston during the remainder of the power stroke.

The construction and assembly of the mechanism of FIGURE 1 is clearly illustrated except that adequate bolting of the outermost place (cap of cylinder 15) to the block should be satisfactory to contain the force produced in the outer dashpots by the deceleraton of piston 2. The threaded receptacle 6 permits the insertion of a spark plug or fuel injector mechanism.

To produce a satisfactory and ei'iicient high capacity compressed air accumulator the various accumulator cylinders should be joined to each other and to a tank of compressed air, all Well insulated to maintain heat within the system. This hot tank is equipped with a pressure relief valve and with an inlet pressure switch which regulates a small air compressor equipped with a magnetic clutch and appropriate check valves. The relief valve should have a greater capacity than the inlet opening into this tank so that no explosive pressure could develop from any malfunction. An additional col tank can be placed in parallel or in series between this hot tank and the compressor so that by automatic or mechanical means pressure is available to the accumulator system to permit starting of compression ignition engines.

The actual factory regulaton of an operating engine (built to utilize only a constant onset pressure and with a properly calculated clearance volume) with such an air pressure accumulator would consist in shorting the inlet pressure switch so that compressed air is constantly entering the hot tank and increasing the pressure of the relief valve until the engine becomes rough in its operation, then lowering the pressure just enough to again have have smooth performance. At this point the pressure of the accumulator is slightly below that of the compression pressure-if a constant clearance volume existed, permitting thereby the accumulator piston to move slightly and reduce its inertia, better permitting the explosive type of combustion. Then the pressure switch is regulated downward slightly past the point of air escaping from the relief valve. Such a regulation approximates both the peak and the trough of the pressure waves induced in the system and requires only the intermittent and rare use of the parasitic compressor.

The most efiicient control of the combustion of engines with variable onset pressures requires the additional use of a constant compression pressure device. A hydraulic system invented by me automatically produces such a pressure and also utilizes an accessory cylinder and piston. This hydraulic device might well be placed across a portion of the block cylinder with its reciprocating piston and a portion of the accumulator cylinder (accomplished by their parallel position in the block with a common wall where in contact) with a passageway between these two adjacent large cylinders at the combustion chamber opening (accomplished by lowering the rings on each piston). The design of the combination of these three cylinders and their pistons requires no inventiveness and might well vary depending upon space requirements, etc. When this hydraulic system is utilized, the high pressure oil system might well be utilized as the source of pressure for the relief valve of the hot tank of the accumulator system thereby controlling both the air and the hydraulic system with the pressure relief valve of the high pressure oil compressor (or intensifier). This also concerns purely technical design and does not require any new inventiveness and is left to the discretion of the engineers of the manufacturer.

What I claim that is new and useful in my invention:

In an internal combustion-type reciprocating piston engine having a combustion chamber, means for allowing a rapid expansion of the combustion space within the chamber during combustion which is followed by a rapid contraction of the combustion space with descent of the reciprocating piston, said means comprising a compartment having a large opening communicating with tie combustion chamber, an accessory piston closing the compartment and movable therein away from and toward the combustion chamber in an oscillating manner, the compartment being provided with dashpots to decelerate this accessory piston at each end of its oscillation; said dashpots supplying a check-valve action by means of a springsupport washer forming the backwall of each dashpot, this washer moving with the accessory piston when the piston is leaving the dashpot, said washer then returning to its position at the back wall of the dashpot, such an action allowing air to enter from the backwall of the said dashpot thereby facilitating the release of the accessory piston from the dashpot, pursuant to entry of compressed air to allow rapid expansion and contraction of the combustion space with each combustion stroke.

References Cit-ed in the file of this patent UNITED STATES PATENTS 2,146,032 Scott Feb. 7, 1939 2,419,450 Howard Apr. 22, 1947 2,500,409 Hawkins Mar. 14, 1950 2,758,582 Humphrcys Aug. 14, 1956 2,769,433 Humphreys Nov. 6, 1956 3,076,440 Arnold Feb. 5, 1963 FOREIGN PATENTS 153,673 Australia Oct. 16, 1953 467,960 France Apr. 9, 1914 1,172,883 France Oct. 20, 1958

Images