WO1982004465A1

WO1982004465A1 - Ingnition chamber for low compression auto-ignition internal combustion engines using low cetane fuels

Info

Publication number: WO1982004465A1
Application number: PCT/US1982/000635
Authority: WO
Inventors: Research Center Inc Kovacs; Geza Kovacs; Mihaly Kovacs; Endre Kovacs; Peter Kovacs
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-06-16
Filing date: 1982-05-13
Publication date: 1982-12-23
Anticipated expiration: 1983-12-16
Also published as: BR8207746A; EP0081549A1

Abstract

Chambre de combustion (40) destinee a etre utilisee dans des moteurs a combustion interne a injection directe ou indirecte et a auto-allumage, qui permet de faire fonctionner ces moteurs avec de l'alcool du commerce sensiblement pur ou autres combustibles a faible indice de cetane et a des taux de compression faibles, cette chambre comprenant un boitier (43) qui est de facon predominante en relation d'echange thermique par convection avec la zone de combustion et qui est pourvue d'une pluralite d'ouvertures (46) qui sont concues et orientees par rapport aux surfaces (47, 48) de celui-ci de facon a creer une circulation d'air pendant la compression, ce courant d'air permettant de rassembler les composants legers d'une partie d'une charge de combustible se dirigeant vers la chambre de combustion et de les concentrer pres d'une zone centrale (50) ou ces composants plus legers generalement plus volatils seront soumis aux temperatures elevees qui y regnent afin de declencher une combustion controlee du combustible restant injecte dans la chambre de combustion du moteur. Selon une variante de mise en oeuvre, les chambres de combustion (80) peuvent etre montees directement sur les parois (73) de la cavite de combustion (72) formee dans la partie superieure du piston (65). La chambre de combustion (80) comprend un boitier (82) pourvu de rangees espacees d'ouvertures (86).Combustion chamber (40) for use in internal combustion engines with direct or indirect injection and self-ignition, which allows them to be operated with substantially pure commercial alcohol or other low index fuels cetane and at low compression rates, this chamber comprising a housing (43) which is predominantly in relation to heat exchange by convection with the combustion zone and which is provided with a plurality of openings (46) which are designed and oriented relative to the surfaces (47, 48) thereof so as to create an air circulation during compression, this air flow making it possible to bring together the light components of part of a load of fuel going to the combustion chamber and concentrating them near a central area (50) where these lighter, generally more volatile components will be subjected to the high temperatures prevailing therein in order to initiate combustion control of the remaining fuel injected into the combustion chamber of the engine. According to an alternative embodiment, the combustion chambers (80) can be mounted directly on the walls (73) of the combustion cavity (72) formed in the upper part of the piston (65). The combustion chamber (80) comprises a box (82) provided with open space rows (86).

Description

IGNITION CHAMBER FOR LOW COMPRESSION AUTO-IGNITION INTERNAL COMBUSTION ENGINES USING LOW CETANE FUELS

Description

Technical Field This invention relates generally to compression ignition internal combustion engines and particularly to an ignition chamber which may be used in direct or indirect compression ignition type engines to enable alcohol fuels including substantially pure commercial grade methanols and ethanols and other low cetaine fuels to be auto-ignited at relatively low compression ratios in order to initiate controlled combustion of such fuels without the requirement of external sources of heat or chemical fuel ignition accelerators once the engine has achieved operating temperature.

Background Art

As shortages have been met in the current availability of petroleum supplies and due to the ever increas ing price of gasoline and diesel fuels traditionally used in internal combustion engines, there has been a continuing emphasis placed on developing alternative sources of automotive fuels. In particular, there has been a great deal of recent effort directed to develop ing the use of alcohol and alcohol base low cetane fuels in internal combustion engines.

Although prior utilization has been made of alcohols in both controlled ignition internal combustion engines and diesel type compression ignition engines, such used have generally required modifications of the fuel mixtures by incorporating therewith more volatile fuel elements including mixtures of gasoline and diesel fuels and/or by the addition of chemical ignition accelerators such as alkyl nitrates and nitrites and ethers. In United States patent 4,216,744 to Oswald et al. there are disclosed fuels containing various percentages of alcohol which are used in controlled ignition engines, which engines operate at compression ratios varying between 12 and 20:1.

It has generally been considered that auto-combus tion of substantially pure commercial grade alcohols such as methanol alone was not practical in a compression ignition diesel type engine as alcohol has an extremely high auto-ignition temperature. The capability of auto-ignition is reflected by the cetane rating of the fuel. Whereas diesel fuels have cetane ratings of approximately 45 to 55, the cetane. rating for methanol is approximately 3 to 5. (The lower the cetane rating, the higher the temperature necessary for auto-ignition). Therefore, prior art engines in which alcohol or other low cetane fuels have been used have required the continuous use of supplemental ignition promotors including glow plugs, spark plugs and incandescent heat exchangers or other types of fuel preheating devices in order to achieve the elevated ignition temperatures necessary for alcohol combustion.

In various prior art high compression injection engines, supplemental auxiliary fuel nixing or precombustion chambers have been utilized incorporating heat retaining or heat supplying elements such as electrical grids and incandescent igniters. Such engines have been operated at compression ratios in the range of 17-20:1. However, in conventional compression ignition systems it has not been possible to utilize substantially pure commercial grade alcohol fuels without some supplemental ignition sources or unless the alcohol vras blended with other more volatile fuel elements. Further, due to the elevated operating temperatures associated with the combustion of low cetane fuels, such preheating elements and incandescent igniters were frequently deteriorated after a short operating life. In addition to the foregoing problems associated with the combustion of low cetane fuels, it is also necessary to maximize the efficiency of engines using such fuels so as to conserve fuel while obtaining optimum engine performance. There has been a great deal of effort directed to modifying primary and supplemental combustion chamber designs as well as modifying other components of diesel engines in order to effect a complete mixing of fuel charges to promote more efficient ignition and thorough burning of the fuel. Again, however, due to the high ignition temperature of low cetane fuels including substantially pure commercial grade alcohols such as methanols, ethanols and the like, together with the heat loss characteristics of prior art compression ignition systems, it has not been possible to auto-combust such fuels without providing supplemental heat sources or more expensive fuel ignition additives.

Disclosure of the Invention

The present invention is embodied in an ignition chamber for use in both direct and indirect compression ignition engines of the diesel type which operate at compression ratios of approximately 10:1 and up and which enables low cetane fuels including substantially pure commercial grade alcohols to be used as a fuel in such engines. The ignition chamber is mounted within a diesel engine in such a position as to receive a portion of the alcohol injected into the cylinder. The ignition chamber is provided with a plurality of tapered ports or openings which are arranged generally tangentially of the inner periphery of the chamber and are located primarily along the area of the maximum diameter thereof, in generally parallel relationship. The total cross-sectional area of the ports should generally be not greater than 5% of the total inner surface area of the ignition chamber.

The ignition chamber may be either mounted in direct communication with the primary combustion chamber within the cylinder or within a suppl emental combustion chamber which is adjacent to and communicates with the primary combustion chamber, however, the ignition chamber is secured to the supporting engine surface so that at least a major portion of the surface thereof is spaced from the adjacent engine surface so as to minimize the conductive heat loss from the ignition chamber while maximizing the convective heat relationship with the surrounding combusion zone.

During the compression stroke of the piston, a mixture of air and a minor portion of the incoming fuel charge is forced through the ports or openings in the ignition chamber and such mixture is accelerated as it is forced therein. The mixture which is heated by compression and by the residual heat retained within the combustion zone is caused to flow around the inner periphery of the ignition chamber, creating a vortex having a dead air zone in the central portion thereof. Due to the configuration of the ignition chamber and the configuration and positioning of the ports, therein, the lighter fuel components, such as hydrogen, which have become dissociated from an injected alcohol fuel due to the temperature within the ignition chamber and which are more volatile, are concentrated within the central portion thereof and are auto-ignited within the ignition chamber. This initial ignition causes a substantially spontaneous combustion of the remainder of the fuel charge in the engine's primary combustion chamber.

It is a primary object of this invention to provide an ignition chamber for use in both direct and indirect injection internal combustion pressure ignition engines so as to enable such engines to operate utilizing low cetane fuels including substantially pure commercial grade alcohols including methanols, ethanols and the like without the continuous need for supplemental or heat exchange sources such as spark plugs, glow plugs or incandescent and electric heat exchangers and without having to blend the low cetane fuel with more volatile combustion agents or chemical ignition accelerators, even when such engines are operated at lower compression ratios in the range of 10:1. It is another object of this invention to provide an ignition chamber for a diesel type direct or indirect injection compression auto-ignition engine wherein the ignition chamber is designed and constructed so as to permit sufficient temperatures to be achieved during the engine's compression stroke to initially cause dissociation of hydrogen from the substantially pure commercial grade alcohols and thereafter cause ignition of the hydrogen at relatively low compressions.

It is a further object of this invention to provide an ignition chamber for a compression ignition engine wherein the openings between the ignition chamber and the main or a surrounding auxiliary combustion chamber are so positioned as to create an increased acceleration of fluid flow into the ignition chamber during compression so as to collect and concentrate the lighter more volatile fuel particles and gas which are dissociated from an alcohol or other low cetane fuel injected into the engine.

It is another object of this invention to provide an ignition chamber for a compression ignition engine which is in open communication to either the main or an auxiliary combustion chamber by way of a plurality of tapered and tangentially oriented openings which are disposed through the side walls of the chamber and in which the maximum area defined by the openings adjacest the the inner surface of the chamber generally will not exceed approximately 5% of the total inner surface wall area thereof and which are further disposed through the wall of the chamber so as to direct the flow in a vortex within the chamber.

It is a further object of this invention to maintain the temperature of the ignition chamber at a sufficient level to cause ignition of the more volatile components of low cetane fuels by reducing the amount of conductive heat loss from the ignition chamber to the walls of the engine or engine components. In this regard, at least 50% to 60% and preferably 80% or more of the exterior surface of the ignition chamber must be spaced from the adjacent walls of the engine head, auxiliary combustion chamber or piston to which it is mounted so as to be substantially in convective heat exchange relationship to the heated air within the main or an auxiliary combustion chamber.

It is yet another object of this invention to provide an ignition chamber which may be mounted within existing direct or indirect injection diesel engines including being mounted to the head, the piston or within an auxiliary combustion chamber to thereby enable such engines to auto-combust low cetane fuels including substantially pure commercial grade alcohols by compression.

It is another object of this invention to increase the efficiency of low cetane or other fuels, consumed in a direct or indirect injection diesel engine by varying the size and number of ignition chambers utilized to create the initial fuel ignition.

Brief Description of the Drawings

Fig. 1 is a fragmentary sectional view illustrating the invention as mounted within an auxiliary combustion chamber of an indirect injection internal combustion engine as the piston approaches the end of the compression stroke.

Fig. 2 is an enlarged fragmentary section of the main and auxiliary combustion chambers and ignition cham ber of Fig. 1 during fuel injection.

Fig. 3 is an enlarged sectional view taken along line 3-3 of Fig. 2 illustrating the flow of gaseous material during compression.

Fig. 4 is a fragmentary section view illustrating the invention as mounted to the head of a direct injection compression ignition engine as the piston approaches the end of the compression stroke.

Fig. 5 is a fragmentary sectional view illustrating a modified form of the invention as mounted to the pis ton of a direct injection compression ignition engine as. the piston approaches the end of the compression stroke.

Best Mode for Carrying Out the Invention With continued reference to the drawings, an internal combustion engine 10 is shown which includes an engine block 11 and a head 12. A head gasket 13 is positioned between the head and the block and the head is connected to the block by a plurality of bolts (not shown). The block 11 has an upper wall 14 with at least erne cylindrical wall 15 extending downwardly therefrom and the inner periphery of such cylindrical wall defines a relatively smooth axial cylinder bore 16. A piston 17 is slidably mounted within the bore 16 and such piston is connected in a conventional manner (not shown) to a crankshaft by a wrist pin and piston rod. The piston includes an upper portion 18 integrally connected to a depending skirt 19 and such piston is provided with a plurality of annular grooves 20 which receive sealing rings 21 which slidably engage the bore 16 of the cylinder. The central portion of the piston head 18 is shown as being relatively flat, however, it may be provided with a recess as shown in Figs. 4 and 5.

The head 12 includes a substantially planar inner wall 23 which is in direct open communication with the cylinder bore 16. A flared or stepped opening 24 is provided through the head 12 so as to be directly above the bore 16 and communicates with a bore 25 which extends outwardly from the cylinder 16. An auxiliary combustion or pre-combustion chamber housing 27 is mounted within the bore 25 and the stepped opening 24 so as to be in intimate sealed engagement with the adjacent wall portions 28 of the head.

As shown in the drawings, the auxiliary combustion chamber housing 27 includes upper and lower portions 29 and 30 which define a generally hemispherical auxiliary combustion chamber 31 therebetween. The lower portion 30 of the auxiliary combustion chamber housing has a stepped angulated channel 32 therethrough which openly communicates the auxiliary combustion chamber 31 with the main combustion chamber disposed between the upper surface of the piston and the lower wall 23 of the head. The channel 32 includes an opening or mouth portion

33 and a wider inner passage 34. As shown by the arrows in Fig. 1, the channel 45 directs air flowing into the chamber 31 about the inner periphery thereof which is defined by the arcuate inner wall 35 of the upper portion 29 of the housing 27.

An opening 36 is provided through the center of the upper portion 29 of the auxiliary chamber housing 27 and a fuel injector 37 is mounted therein so as to be generally aligned with the elongated central axis of the auxiliary combustion chamber 31 and the passage

34 of the channel 32. In this manner , fuel being inj ected through the auxiliary combustion chamber and the channels into the primary combustion chamber will pass either directly through channel opening 33 or be deflected angularly outward between the piston and cylinder head as indicated by the dotted lines in Fig. 2.

As previously discussed, it is the primary purpose of this invention to provide for the low compression auto-combustion of low cetane fuels and particularly substantially pure commercial grade alcohols. In this regard it has been determined that if a portion of an injected alcohol fuel charge be dissociated to separate the more volatile hydrogen therefrom and thereafter the lighter hydrogen gases concentrated in one area, that the hydrogen could be ignited under controlled conditions at lower temperatures and pressures. Such preliminary or initial ignition could therefore be used to initiate complete combustion of the remainder of the alcohol fuel charge.

To affect the concentration of the hydrogen and to create residual temperatures which will support ignition of the hydrogen, an ignition chamber 40 is mounted within a semi-spherical opening or pocket 41 in the peripheral side of wall 35 of the auxiliary combustion chamber 31. The ignition chamber 40 includes an elongated base portion 42 and spherical head or housing 43. The base 42 is securely mounted within a bore 44 through the upper portion 29 of the auxiliary combustion chamber housing 27 so that the head 43 is disposed outwardly into the auxiliary combustion chamber 31 in spaced relationship with the inner walls 35 thereof. A second bore or opening 44' extends through the upper portion of the auxiliary combustion chamber adjacent the semispherical pocket 41 and such bore receives a glow plug 45 for purposes as will be hereinafter described in greater detail.

With particular reference to Figs. 1-3, the igninition chamber 40 includes a plurality of spaced openings 46 which are tapered inwardly between the outer surface 47 and inner surface 48 of the ignition chamber 40. Further, the innermost portion 49 of each opening is shown as being generally tangentially oriented with respect to the inner surface 48 thereof. It should be noted that the openings 46 lie in substantially the same plane and that such plane should preferably be defined by a line taken through or adjacent the maximum diameter D of the head or housing 43 of the ignition chamber. As the openings are tapered inwardly between the inner and outer surfaces of the head with the innermost portion of the openings or ports 49 being oriented so as to be generally tangential to the inner wall 48, the incoming air is not only accelerated as it enters the ignition chamber, but is also directed along the inner periphery thereof in a circular pattern. Such flow will create a vortex having a dead air space 50 along or defining the axis thereof, which axis extends perpendicularly to, and centrally of, the circular flow path.

With respect to the injection of fuel into the combustion zone defined by the main and auxiliary combustion chambers, the injector 37 may be one such as that described in applicants' prior United States patent 4,005,685 to which a modified nozzle 51 has been added. With particular reference to Fig. 2, the fuel injector nozzle is designed to separate the injected fuel into two streams. The first or main stream F is injected directly toward the opening 33 of the channel 32 of the auxiliary combustion chamber housing 27 while a lesser quantity of fuel is simultaneously injected, as shown by stream F₂ toward the openings 46 into the ignition chamber. In this regard, it has been determined through a series of tests that the most efficient use of the fuel is made when not more than approximately 10% of the injected fuel is injected into the ignition chamber. The use of greater quantities of fuel in stream F₂ could result in greater fuel consumption and less efficiency in the power stroke. Generally, it is preferred to direct as much of the fuel as possible directly toward the main combustion zone whereby the fuel will be combusted in direct relationship to the piston.

Due to the circular flow of air in the ignition cham ber when fuel is injected through the openings 46, the heavier particles of fuel entrained in the air are forced outwardly by centrifugal action while the lighter or less dense particles are collected or concentrated inwardly toward the dead air zone 40. When low cetane fuels such as alcohol are injected the hydrogen dissociates from the alcohol in the ignition chamber, and it is believed that the light hydrogen particles or gases are concentrated adjacent the dead air zone. The concentrated hydrogen adjacent the dead air zone will be subjected to elevated residual temperatures sufficient to cause auto-ignition of the hydrogen. The initial combustion or initial ignition will in turn cause the remaining alcohol in the auxiliary and main combustion chambers to ignite expanding the gases in these combus tion areas and driving the piston downwardly. In this manner, it is possible to obtain a controlled auto-combustion of low cetane fuels and particularly substantially pure commercial grade alcohol fuels such as a methanol or ethanol in a compression ignition engine. Although the preferred embodiment in Figs. 1-3 discloses the use of a plurality of generally equally spaced converging or tapered openings 46 arranged in a single row, other opening configurations including multiple rows of openings may be used. If the openings are to be spaced in different planes, they should lie as close as possible to the area or plane defining the maximum diameter D of the housing, thereby generating a maximum circular flow path. In determining what configuration is to be used, it is necessary to insure that the air flow within the head 43 of the ignition chamber 40 be of a sufficient velocity and in an appropriate pattern to cause the dissociated hydrogen gases to be collected or concentrated in one area of the ignition chamber. The flow pattern should be nonturbulent within the ignition chamber, therefore no opening should direct the incoming air and fuel through the center of the ignition chamber as this would effectively destroy the centrifugal flow pattern which causes the hydrogen to be collected adjacent the central dead air zone. Preferably, all openings should be oriented in substantially parallel relationship so that the incoming air and fuel are directed in parallel flow paths about a common axis.

In utilizing the spherical ignition chamber, it has been determined that in order to create a sufficient centrifugal velocity within the head that the number and size of the openings as measured at the innermost portion thereof, as at 49, should generally not exceed a total surface area of greater than 5% of the total inner surface area of the head or housing 43. In tests made utilizing a modified YSE-12 YANMAR single piston marine diesel engine having a piston diameter of 3.45 inches (87.63 mm), a 3.550 inches (90.17mm) stroke and a 10 horsepower rating, it was found that although the engine could be operated at higher RPMs, i.e., 2,000 RPM or more, utilizing an ignition chamber head in which the total opening space was approximately equivalent to 7%-10% of the inner surface area of the ignition chamber, that the same engine could not be operated smoothly at lower RPMs. It is further believed that if the shape of the ignition chamber housing is changed, such as to be providing a cylindrical configuration having openings disposed through the periphery thereof, that the percent of the surface area of the openings to the internal surface area may be less than 5%. As previously mentioned, the residual temperatures in the ignition chamber must be sufficient to cause auto-ignition of the concentrated or collected lighter and more volatile gases. In the preferred embodiment shown in Figs. 1-3, it can be observed that the exterior surface area available for conductive heat loss to the surrounding engine head has been minimized by providing an elongated base or mounting portion 42. Thus, the majority of the surface area of the ignition chamber is directly exposed to the heated air and gases within the auxiliary combustion chamber 31 and the convective heat loss to the surrounding heated air and gaseous media is less than if a corresponding surface area were in conductive heat exchange relation ship with the metallic head of the engine. Additionally, it is theorized that the residual temperature in the dead air zone created by the circular flow of air and gas within the ignition chamber is maintained at even a higher elevation than would otherwise be possible if the flow of air and gas were simply turbulent, thereby disrupting any dead air space.

As previously discussed, it is preferred that only a minor portion of the incoming fuel charge be directed toward the housing of the ignition chamber. This directed fuel, which may be an alcohol, will tend to cool the housing and in so doing will reduce the damage caused by excessive heat buildup which would shorten the operating life of the ignition chamber. In practice, it is believed that the temperatures within the ignition chamber fluctuates, during engine operation, between approximately 1000°F -1400°F. Due to the high temperature and impacting fuel sprays, the ignition chamber should be manufactured from material which is both resistant to high temperatures and corrosion.

With particular reference to Fig. 4, two ignition chambers 40 are shown as they are mounted to the head 61 of a direct injection type compression ignition engine 62. The ignition chambers are the same as described with respect to Figs. 1-3 and include the same annularly disposed tapered openings 46. The direct injection engine 62 includes a cylinder wall 63 defining a bore 64 in which a piston 65 is reciprocally mounted. The piston includes an upper surface 66 and depending skirt portion 67. An opening 68 is provided through the head 61 in which an injector 69 is mounted. The injector includes a nozzle 70 which directs a portion of the fuel charge outwardly toward the housings 43 of the ignition chambers 40.

As each of the ignition chambers is mounted having its base portions 52 within spaced openings 71 in the head 61, the housings 43 of the ignition chambers will be disposed downwardly towards the upper surface 66 of the piston. In this embodiment, a conventional shaped combustion cavity 72 is provided in the upper portion of the piston. The cavity is defined by arcuately and concavely shaped peripheral walls 73 which are connected along their lowermost portions by a somewhat inverted conical surface 74 which includes an upstanding central tip portion 75. The clearance provided by the peripheral walls 73 of the combustion cavjty 72 is sufficient to permit the housings 43 of the ignition chambers to be disposed within the cavity when the piston reaches top dead center position.

Although two ignition chambers are shown in Fig. 4, the engine may be operated by combusting low cetane fuels including substantially pure commercial grade alcohols utilizing one or more such chambers. By utilizing two or more spaced ignition chambers within the combustion zone or cavity, it is possible to create a more even or uniform ignition and subsequent combustion of the fuel charge.

With particular reference to Fig. 5, a modified form of ignition chamber 80 is disclosed. The direct injection engine 62 is the same as that described with respect to Fig. 4 except that the modified ignition chambers are shown as being mounted within openings 81 horizontally disposed in the side or peripheral walls 73 of the combustion cavity 72 formed in the upper portion of the piston 65. Each ignition chamber 80 includes a head or housing portion 82 and a base portion 83. The base portion includes an opening 80 therein by way of which a locking pin 85 may be selectively positioned therethrough to secure the ignition chambers within the openings 81. Each of the ignition chamber housings 82 includes two series of annularly disposed generally equally spaced openings 86 which openings are oriented in two parallel vertical planes, there being twelve such openings shown in each housing. Again, the number of openings and their respective placement may vary as previously discussed. As with the embodiment of Fig. 4, the injector 69 in Fig. 5 includes a nozzle 70 for directing at least a portion of the fuel spray towards each of the ignition chambers.

With respect to the injection of a portion of the fuel charge toward the ignition chamber, this is done in order to increase the relative concentration of fuel to air within each ignition chamber. Preferably, the concentration of fuel within each ignition chamber is

40%-80% greater than that of the surrounding combustion zone. However, it is also preferred not to direct more than approximately 10% of the incoming fuel away from the primary combustion zone. It should be apparent that only a minimum amount of the incoming fuel should be used to initiate combustion. Therefore, the smaller the quantity of incoming fuel that is dissociated and collected in the ignition chambers, the more efficient the fuel economy will be. Further, although the ignition chambers shown in the drawings appear to be quite sizable with respect to the primary combustion-zone, in practice it has been determined that in some engines the ignition chambers may actually be of a size defining a volume which is as small as 1% of the total combustion zone or chamber. In order to provide optimum fuel efficiency, an effort should be made to use the smallest possible ignition chamber which will still support controlled combustion of the remaining fuel charge.

Although not shown with respect to Figs. 4 and 5, it is necessary that either a glow plug similar to that disclosed in Figs. 1-3 be provided and either be directly exposed to the gases within the ignition chamber or be mounted so as to be disposed directly adjacent the exterior wall thereof and adjacent an opening leading therein or that some supplemental ignition assistant or accelerator be used during the initial engine operation. As it is necessary that the residual heat within the ignition chamber be sufficiently high to ignite the lighter particles or gases collected therein, it is only necessary that a supplemental source of heat or chemical accelerator be provided until the engine has reached operating temperature. Thereafter, due to the design characteristics of the present ignition chambers, the residual temperatures within the dead air zone will be maintained at a sufficient level to cause auto-combustion of low cetane fuels such as methanols and ethanols by compression utilizing the initial ignition of the collected hydrogen or other lighter more volatile dissociated fuel components to initiate the combustion of the remaining fuel charge. In the operation of the internal combustion compression ignition engine of the present invention, air or other gases which have been introduced into the cylinder through the intake valve are compressed by the upward movement of the piston and thereby forced through the tapered openings of the ignition chamber. As compression continues, the air entering the ignition chamber is not only heated by the compression, but is heated as well by the residual heat retained within the ignition chamber. In order to reduce the amount of heat loss from the ignition chamber, it is necessary that the major portion of the surface area of the head of the ignition chamber be spaced from the adjacent walls of the engine head or piston to thereby reduce conductive heat losses between the ignition chamber and other engine components. Generally, at least 80% of this surface area should be so spaced.

Due to the tapered or converging configuration of the air openings or ports into the ignition chamber, the air and fuel entering therein is accelerated and as shown in Fig. 3, such air enters the chambers at a high velocity and is directed generally tangentially to the inner walls thereof. In this manner, the air within the ignition chambers follows a substantially circular path.

When the piston is close to the end of its compres sion stroke, which, depending upon the type of engine and the kind of burning chamber, may be anywhere from 6°-25° below top dead center, a low cetane fuel such as an alcohol is injected under pressures exceeding 1800 p.s.i. through the injector nozzle. At least a portion of the fuel is injected toward and into the ignition chamber or chambers. When the alcohol fuel such as a methanol or ethanol passes through the opening, such fuel begins to dissociate and the lighter fuel particles are collected or concentrated within the air moving about the dead air zone. The lighter particles of fuel are subjected to the high temperature within the dead air zone and the combustible mixture is ignited. During the initial cranking, additional heat will be provided by the glow plug, however, when the engine reaches operating temperature, the glow plug is disconnected from the power source. As combustion continues within the main combustion chamber, the rapidly expanding gases force the piston downwardly toward the bottom dead center position.

It should be emphasized that it is necessary to both retain sufficient residual heat within the ignition chambers to permit auto-ignition of the lighter fuel particles collected therein and to create a great enough centrifugal flow of particles within the ignition chamber to concentrate or collect such particles adjacent the central dead air zone. With regard to creating the required air flow within the ignition chamber, the openings therein should be: tapered to cause acceleration of particles; tangentially oriented with respect to the inner surface of the ignition chamber; disposed in such a relationship as to create a flow about a single axis through the ignition chamber and be preferably located adjacent the maximum diameter of the ignition chamber so as to insure a continuous dead air zone therethrough; and the total or aggregate of the inner cross-sectional areas of the openings should not exceed generally 5% of the total inner surface area of the ignition chamber.

Industrial Applicability Due to the ever increasing costs of the more conventional petroleum based fuels and the continuing detrimental effects upon the ecology created by the use of such fuels, it has become necessary that alternative sources of energy be utilized in internal combustion engines. In this regard, there has been a great deal of effort directed toward developing technologies which will permit the use of readily obtainable resources such as alcohols which can be manufactured from forestry and agricultural waste materials to be used in powering internal combustion engines.

To date, most efforts have required blending alcohol or other low cetane fuels with other more volatile fuels including gasoline and diesel fuel and the like in order to provide for the ignition of such fuels. As previously discussed, problems have been encountered in using substantially pure commercial grade alcohols in both con trolled ignition and diesel engines including incomplete combustion, sporadic combustion caused by preignition of separated or dissociated more volatile components of the fuel charges, the added costs and problems inherent in using supplemental heat sources or heat ex changers, and maintaining fuel blends in a miscible state.

With the ignition chambers used with the present invention, it is possible to use substantially pure commercial grade alcohols including methanols and ethanols and the like as the sole source of fuel in a compression ignition engine without the need to provide continuous supplemental heat exchangers, chemical fuel combustion accelerators or supplemental ignition means after the engine has reached operating temperature. Further, as it has been found that substantially pure commercial grade alcohols can be auto-combusted at low compression ratios of 10:1 and up using the teachings of the present invention, it is possible to save wear and tear on engine components. it. has also been determined that the ignition chambers of the present invention may be used in conventional direct and indirect type diesel engines which are powered by diesel and gasoline fuels. The use of ignition chambers will permit such conventional diesel engines to be operated at lower compression ratios than would otherwise be possible and would also significantly reduce wear on engine components.

Claims

1. An ignition chamber for use in internal combustion pressure ignition engines comprising a mounting portion and a housing, said housing extending outwardly from one end of said mounting portion and having inner and outer surfaces, a plurality of openings disposed through said housing between said inner and outer surfaces, each of said openings being substantially tangentially oriented with respect to said inner surface of said housing, each of said openings being substantially oriented so as to direct fluid passing therethrough about a common axis through said housing, and the combined total of the cross-sectional surface areas of said openings taken at said inner surface of said housing not exceeding approximately 5% of the total inner surface area thereof.

2. The invention of claim 1 in which said inner and outer surfaces include generally arcuately shaped peripheral portions which define a maximum diameter of said housing, and said openings being disposed in spaced relationship about said housing generally along the plane defining said maximum diameter of said housing.

3. The invention of claim 2 in which said housing is generally spherical.

4. The invention of claim 3 in which said openings through said housing are disposed in at least two parallel planes.

5. The invention of claim 2 in which said openings within each plane are substantially equally spaced with respect to one another.

6. The invention of claim 1 in which each of said openings through said housing is reduced in cross section from said outer surface to said inner surface of said housing.

7. In an internal combustion compression ignition engine having a block and a head, at least one wall defining a cylinder in said block, a piston mounted for reciprocal movement along said cylinder and a combustion chamber, the improvement comprising at least one ignition chamber having a housing defined by a generally arcuately shaped side wall having inner and outer peripheral surfaces, a plurality of openings disposed through said side wall which provide fluid communication between an internal volume defined within said housing of said ignition chamber and the com bustion chamber, each of said openings being tapered along its length so as to be of a reduced cross-sectional dimension adjacent said inner peripheral surface of said side wall and being arranged tangentially with respect to said inner peripheral surface of said side wall so that fluid entering said housing of said ignition chamber under pressure is accelerated into a circular flow path therein which creates a dead air zone along an axis of said ignition chamber, the cumulative surface area of said openings taken at said inner surface of said ignition chamber not exceeding approximately 5% of the total surface area of the total inner surface thereof, and injector means, said injector means directing a portion of the fuel passing therethrough toward and into said housing of said ignition chamber during compression so that the concentration of fuel within the ignition chamber is greater than the concentration of fuel within the combustion chamber as the piston approaches top dead center position.

8. The invention of claim 7 in which said openings are disposed in substantially equally spaced generally parallel relationship along at least one plane adjacent the maximum diameter of said inner peripheral surface of said side wall.

9. The invention of claim 7 in which at least approximately 80% of said outer surface of said housing is in convective heat relationship with the combustion chamber.

10. The invention of claim 9 in which said ignition chamber includes a base portion which is mounted to the head.

11. The invention of claim 9 in which said ignition chamber includes a base portion which is mounted to the piston.

12. The invention of claim 9 in which the combustion chamber includes an auxiliary combustion chamber and wherein said ignition chamber is mounted within said auxiliary combustion chamber.

13. The method of auto-igniting alcohol in an internal combustion compression ignition engine having a block and a head and a piston reciprocally movable within a cylinder, a combustion chamber and an ignition chamber mounted within the head and having openings which communicate the ignition chamber with the combustion chamber including the steps of:

(a) compressing air within the cylinder,

(b) accelerating said compressed air into the ignition combustion chamber during compression,

(c) directing said accelerated air in a circular pattern within said preliminary ignition chamber to thereby create a dead air zone centrally thereof wherein elevated temperatures are maintained,

(d) injecting a first portion of alcohol fuel charge into the combustion chamber at a period close to the end of the compression stroke, and simultaneously directing a second portion of said alcohol fuel charge toward said ignition chamber to thereby entrain said second portion with said accelerated air within said ignition chamber and collecting the hydrogen being dissociated from the alcohol due to the high temperatures within said ignition chamber, and (e) igniting the collected hydrogen within the ignition chamber to thereby initiate combustion of the remaining alcohol charge within the combustion chamber.