Abstract:
An apparatus and method for improving efficiency of combustion engines. At least two combustion chambers are provided by contouring the surface of a piston or a cylinder head or a combination thereof. Such a contoured piston or cylinder head controls the peak temperature and pressure in order to combust the mixture efficiently, to increase power generated, and to decrease the amount of unused mixture exhausted from the combustion chamber. With the ability to control the peak pressure, the ignition plug can be fired at advanced ignition timing, thereby extending its life. The chambers are also designed to control flame propagation speed to reduce knock. Additionally, the chambers can also decrease the amount of pollutants such as NO x  produced during combustion.

Description:
GOVERNMENT RIGHTS IN THIS INVENTION 
     This invention was made with U.S. government support under contract number DAAE 07-95-C-R081, PS0013. The U.S. government has certain rights in this invention. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the invention generally relate to an apparatus and method of use in an internal combustion engine. More particularly, embodiments of the invention relate to a combustion chamber design that physically segregates the chamber into multiple smaller chambers during combustion in a combustion engine. 
     2. Description of the Related Art 
     Conventional combustion, reciprocating engines are widely used as automotive engines. These engines are designed to work on a predetermined mixture of air and fuel, which is ignited by an ignition plug, such as a spark plug or a glow plug, in a combustion chamber. 
     FIG. 1 is a cross-sectional view of a conventional power cylinder assembly  50 . The power cylinder assembly  50  includes a cylinder  110 , a piston  100 , a cylinder head  117 , valves  140  and  150 , an ignition plug  160 , and manifolds  145  and  155 . A combustion chamber  115  is defined by an inner wall  111  of the cylinder  110 , the crown or top surface  107  of the piston  100 , along with the cylinder head  117 . The piston  100 , which is slideably disposed in the cylinder  110 , and the inner wall  111  of the cylinder  110  are generally cylindrical in shape. The piston  100  includes several compression seals  120  (commonly referred to as piston rings) disposed within annular grooves  122  on an outer surface  124  of the piston  100  to keep the fuel/air mixture (hereinafter “mixture”) within combustion chamber  115 . Additionally, the piston  100  includes an aperture  105  for connecting the piston to a connecting rod (not shown), whereby the piston may be moved in a reciprocating fashion (e.g., axially within the cylinder  110 ). The movement of the piston  100  is translated to the rod, which provides power to an engine crank shaft (not shown). The intake manifold  145  delivers the mixture to the combustion chamber  115  and the intake valve  140  regulates the amount of mixture that enters the chamber. The ignition plug  160  ignites the mixture in the combustion chamber  115  and produces a combustion flame. The exhaust valve  150  and the exhaust manifold  155  exhaust the burned mixture and any remaining mixture from the chamber  115 . 
     Typically, an engine cycle starts with an intake stroke, wherein the mixture is delivered into the combustion chamber  115 . During the intake stroke, the piston  100  descends to bottom dead center or the lowest point that the piston may travel in the cylinder  110 . At this point, the intake valve  140  opens and supplies the combustion chamber  115  with the appropriate amount of mixture through the intake manifold  145 . During the intake stroke, the exhaust valve  150  remains closed. As the mixture enters the combustion chamber  115 , a swirl, which mixes the air and fuel, is created by the positioning of the intake valve  140  at a certain angle in the cylinder head  117 . Further, the swirl may be utilized to create turbulence for combustion enhancement. After the piston  100  reaches bottom dead center, the intake valve  140  is closed and ends the intake stroke. The compression stroke begins when the piston  100  ascends in the cylinder  110 . The compression stroke compresses the mixture for better combustion. In the compression stroke, the piston  100  ascends in the cylinder  110  and causes the mixture to squish or move radially inward, causing a squish flow. The squish flow helps to promote faster combustion by enhancing flame propagation. Before the piston  100  reaches top dead center, or the highest point that the piston can travel in the cylinder, an ignition plug  160  is fired to ignite the mixture. In diesel engines, no ignition plug is present, but instead, ignition can occur when the compression pressure and temperature in the chamber is sufficient to support ignition. The pressure and temperature in the combustion chamber  115  are increased by the burning mixture and the pressure forces the piston  100  to descend during the expansion stroke, which moves the connecting rod to power the engine. The expansion stroke provides power to the engine. The piston  100  reaches bottom dead center and ends the expansion stroke. The exhaust stroke, which removes the combusted mixture from the chamber  115 , begins when the piston  100  ascends in the cylinder  110 . As the piston  100  ascends, the exhaust valve  150  opens to remove the combustion by-products and any remaining mixture through the exhaust manifold  155 . The cycle is then repeated. 
     The efficiency of the combustion chamber to combust the mixture determines the amount of pollutants such as oxides of nitrogen or NO x  that are released into the atmosphere. To achieve higher efficiency using hydrocarbon fuels, leaner fuel to air ratios have been utilized. For equivalent power output, a leaner fuel to air ratio must be accompanied by a higher over-all airflow to the engine. The leaner fuel to air ratio leads to high thermal efficiencies, when the airflow has been compensated, and to higher peak temperatures. At higher peak temperatures, combustion efficiency improves at the expense of increased production of NO x . It is known that above 1300-1500° K. (Kelvin), NO x  production increases greatly; hence it is desirable to control the peak temperature below this range. Additionally, faster flame propagation speed increases engine thermal efficiency, but can cause knock (commonly referred to as auto ignition). Knock occurs when the chemical kinetic reactions within the unburned mixture spontaneously ignite during the engine cycle. Typically, knock is initiated by compression of the unburned mixture during the combustion portion of the engine cycle. After the spark ignition process, the unburned mixture is subjected to compression by the combined effects of piston&#39;s motion and flame propagation. If the flame produced by the ignition plug fails to consume the entire unburned mixture before compression-induced chemical reactions cause spontaneous ignition within the unburned mixture, knock will occur. Hence, control of the propagation of the flame has a direct impact on the propensity for a given engine to knock. Knock decreases combustion efficiency because the energy created during auto ignition is uncontrolled and can lead to catastrophic engine failure. 
     In a conventional combustion chamber, the squish region, where squish flow is created, may be up to 70% of the crown&#39;s surface and is a continuous region. Because the squish region is one, large continuous area, there is more area for a flame to lose energy into the piston and quench due to wall heat transfer losses. Additionally, the flame tends to extinguish by the time it reaches the outer portion of the squish region, thereby leaving some mixture unburned leading to combustion inefficiency. 
     In engines, a brake mean effective pressure (BMEP) is generated within the combustion chamber as a resultant pressure force produced from the controlled burning of the mixture. High BMEP is associated with high power output and high engine efficiency. In conventional high BMEP applications, the ignition plug is fired at a relatively high pressure and temperature. However, firing at higher pressure decreases the life of the ignition plug. In order for the ignition plug to last longer, it should be fired at a lower pressure than the pressure required in conventional engine designs used in high BMEP applications. However, if the ignition plug is fired at a lower pressure or earlier ignition timing (advanced ignition timing), the productions of knock and NO x  emissions increase. 
     Various attempts have been made to improve combustion chambers for use with lean mixtures to reduce concentrations of NO x  and knock. U.S. Pat. No. 5,224,449 discloses using a toroidal chamber on the crown of the piston, whereby a mixture is ignited in the main chamber then reaches the toroidal chamber and ignites the fuel in the toroidal chamber. The pressure in the toroidal chamber increases, whereby a combustion jet gas is shot into the main chamber causing a turbulence that mixes and combusts the mixture. However, the temperatures and pressures produced in the toroidal chamber are so great, that damage to the toroidal chamber of the piston, may occur, leading to catastrophic engine failure. Additionally, the high flame temperature can&#39;t be controlled leading to increased NO x  production. U.S. Pat. No. 4,920,937 includes a combustion chamber having a squish region for generating a squish flow. The squish flow helps to propagate flame speed from the spark plug to the main chamber for better combustion efficiency. However, the increased flame speed can increase undesired knock and decrease engine efficiency. Additionally, because the squish area of the squish region is relatively large, the flame can extinguish before reaching the mixture remaining in the squish region, leading to increased uncombusted or unburned hydrocarbons. 
     Therefore, there is a need for a combustion chamber that can efficiently combust a fuel/air mixture, while reducing the production of air pollutants. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention generally provide for an improved method and combustion chamber for use in a combustion engine that is segregated into multiple chambers to control peak pressure and temperature and to control flame propagation speed to reduce knock. 
     In one embodiment, a combustion apparatus having a combustion chamber is provided. The combustion chamber preferably includes a cylinder having an inner wall and a cylinder head, and a piston disposed in the cylinder. The piston preferably has a top surface having at least a first and a second chamber being concentric about a central axis of the piston. The first and second chambers can be annular recessed grooves, circular recesses or a combination thereof. An inner annular portion is formed between the at least first and the at least second chambers. Additionally, an outer raised portion is formed between the at least second chamber and a perimeter of the piston. The combustion apparatus further includes an intake valve and an intake manifold disposed in the cylinder head and in communication with the combustion chamber. Further, an exhaust valve and exhaust manifold are disposed in the cylinder head and in communication with the combustion chamber. Additionally, an ignition device is disposed in the cylinder head and extends into the combustion chamber. 
     In another embodiment, a piston for an internal combustion engine is provided and preferably includes a cylindrical body that has a surface that defines a region of a combustion chamber, wherein the surface includes at least one circular recessed portion and at least one annular recessed groove being concentric about a central axis of the cylindrical body. The at least one circular recessed portion may be separated from the at least one annular recessed groove by an inner annular raised portion. Additionally, the at least one annular recessed groove is separated from a perimeter of the surface by an outer annular raised portion. 
     In still another embodiment, the piston includes a surface that defines a portion of the combustion chamber. The surface includes a chamber that has a partition dividing the chamber into approximately equal sized first and second chambers. The partition can act as flame control portion that directs the flame from one chamber into another and controls the flame propagation speed. 
     In a further embodiment, a combustion apparatus is provided having a cylinder head that includes a surface that defines a combustion chamber. The surface can include at least one circular recess and at least one annular recessed groove being concentric about the central axis of the cylinder head. The at least one circular recess may be separated from the at least one annular recessed groove by an inner annular raised portion. Additionally, the at least one annular recessed groove is separated from a perimeter of the surface by an outer annular raised portion. 
     In still a further embodiment, an apparatus for use in a combustion engine is provided that includes a cylinder head having a surface defining a portion of a combustion chamber, the surface having a chamber formed therein. A partition divides the chamber into approximately equal sized first and second chambers. The partition can act as a flame control portion that directs the flame from one chamber into another and controls the flame propagation speed. 
     A method for efficiently combusting a mixture of fuel and air in a combustion chamber is also provided and can include the steps of admitting a mixture of fuel and air into the combustion chamber having a surface that includes at least a first chamber concentric with a central axis of the surface and at least a second chamber concentric with the central axis; and controlling a peak temperature and pressure of the combustion chamber by first igniting the mixture in the at least first chamber and producing a combustion flame, then igniting the mixture in the at least second chamber by the combustion flame thereby, producing the peak temperature and pressure in the combustion chamber. The method can also include controlling the flame propagation speed to reduce knocks and pollutants, with the inner and outer annular raised portions and their walls, and can further include controlling turbulence within the combustion chamber by providing separate squish portions designed to optimize turbulence in each of the separate combustion chambers. The method can also include controlling the peak temperature and pressure to decrease the production of pollutants by maintaining the temperature less than about 1,300° K. to 1,500° K. and/or by establishing a size and shape of the at least first and second chambers. By controlling the peak temperature and pressure, the life the ignition plug can increase by firing it at lower peak pressure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the above recited embodiments of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. 
     It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
     FIG. 1 is a cross-sectional view of a conventional power cylinder assembly. 
     FIG. 2 is a cross-sectional view of one embodiment of a power cylinder assembly. 
     FIG. 3 is a perspective view of one embodiment of the piston. 
     FIG. 4 is a cross-sectional view an alternative power cylinder assembly. 
     FIGS. 5 a-d  shows various embodiments of the configuration of the cylinder head along line  5   a — 5   a  of FIG.  4 . 
     FIG. 6 is an perspective view of an embodiment of a piston of the present invention. 
     FIG. 7 is a cross-sectional view along line  7 — 7  of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 2 is a cross-sectional view of one embodiment of a power cylinder assembly  300 . The power cylinder assembly  300  preferably includes a piston  200  preferably slidably disposed in a cylinder  210 , and a cylinder head  217  disposed above the piston  200 . A combustion chamber  215  defined by a crown  207  of the piston  200 , the inner wall  212  of cylinder  210 , and the cylinder head  217 . The cylinder head  217  includes a cylinder base  219 , an intake manifold  245  and an intake valve  240  that are in communication with the combustion chamber  215 . Additionally, the cylinder head  217  includes an exhaust manifold  255  and an exhaust valve  250  that are in communication with the chamber  215 , and an ignition plug  260  disposed above the combustion chamber  215 . The intake valve  240  (shown in the closed position) controls the amount of mixture that is delivered into the combustion chamber  215  from the intake manifold  245 . The mixture can be ignited by the ignition plug  260  in the cylinder head  217 . After the mixture is ignited, the remaining unburned mixture and exhaust from the combustion chamber  215  are released to the exhaust manifold  255  through the exhaust valve  250  (shown in the closed position). The intake valve  240  and exhaust valve  250  may be ports in smaller engines. Furthermore, some engines may comprise multiple intake and exhaust valves. 
     The piston  200  includes annular grooves  222  that houses one or more compression seals  220  (or piston rings) around an outer surface  224  to keep the mixture within the combustion chamber  215 . Additionally, the piston  200  may include an aperture  205  for connecting the piston to a connecting rod (not shown), whereby the piston is moved in reciprocating fashion and transfers the power that is generated to the rod, which in turn transfers power to an engine crank shaft (not shown). 
     In one embodiment of FIG. 2, the piston  200  preferably includes the crown  207  having a main chamber  230  formed in the center thereof. The main chamber  230  can be constructed and arranged to hold a defined volume of mixture therein. The main chamber  230  is preferably a circular recess having a wall  234 . A secondary chamber  235 , preferably an annular recessed groove having a wall  239 , formed outwardly of the main chamber  230  and coaxial therewith. The main chamber  230  and secondary chamber  235  may be concentric about a central axis of the piston  200 . The secondary chamber  235  may also be constructed and arranged to hold a defined volume of mixture therein. The main and secondary chambers mean a cavity, recess, groove or the like that is capable of receiving or holding the mixture. Additionally, the main chamber can be the chamber that may be ignited by the ignition plug, while the secondary chamber can be another chamber or chambers that a combustion flame will travel to after being ignited in the main chamber. The main chamber  230  and the secondary chamber  235  can temporarily segregate the combustion chamber  215  into two chambers when the piston  200  reaches top dead center. 
     The secondary chamber  235  may be separated from the main chamber  230  by an inner annular raised portion  232 . An outer annular raised portion  237  can be formed between the outside wall of the secondary chamber  235  and a perimeter of the crown  207  of the piston  200 . The inner annular raised portion  232  and the outer annular raised portion  237  are also known as squish regions. By providing smaller squish regions  232 ,  237 , less energy is lost to the piston  200 , thus allowing for a decreased flame speed without total flame quench. Because the inner and outer annular raised portions  232 ,  237  decrease the flame speed, they are also flame control portions. 
     In operation, the intake and exhaust valves  240 ,  250  are initially closed. The piston  200  descends to bottom dead center of the cylinder  210  during the intake stroke. The intake valve  240  opens during the intake stroke, thereby allowing the lean mixture to enter from the intake manifold  245  into the combustion chamber  215 . The mixture enters the main chamber  230  and the secondary chamber  235 . After the piston  200  reaches bottom dead center, it ascends during the compression stroke and the intake valve  240  is closed. As the piston  200  reaches top dead center, the mixture is pressurized and the plug  260  ignites the mixture in the main chamber  230 . Because the predetermined volume of the mixture that is trapped by the main chamber  230  is smaller than conventional combustion chambers, the peak combustion pressure and temperature occurring in the main chamber  230  can be limited or controlled to levels at or below a conventional chamber. 
     When the mixture is ignited, a flame is produced and propagates in the main chamber  230  where a peak temperature and pressure are produced. However, the peak temperature and pressure are controlled by the limited volume of mixture available to burn at this point. In addition to controlling the peak temperature and pressure through the volume of the chamber  230 , the flame propagation speed can be controlled by the slope or contour of the wall  234  of the main chamber  230  and by the inner annular raised portion  232 . As noted above, at fast flame propagation speed, the flame compresses the mixture in front of it, thereby increasing the temperature and pressure to cause knock. Here, the flame can travel radially from the main chamber  230 , up the wall  234 , across the inner annular raised portion  232 , in order to combust the mixture in the secondary chamber  235 . The inner annular raised portion  232  is constructed and arranged to slow down the flame (but not quench), because the flame must travel through the predetermined quenching distance or the length of the portion  232 , to reach the secondary chamber  235 . By controlling the flame propagation speed, the propensity for knock is reduced, leading to more efficient combustion of the mixture. As noted above, at combustion temperature above 1300-1500° K., there is a noted increase in the NO x  production. By controlling the peak temperature so that it does not stay above or reach 1300-1500° K., the production of undesired NO x  is reduced. Additionally, the amount of energy lost to heat transfer into the piston can be limited by the area provided for the annular raised portions  232 ,  237 . Further, because the inner annular raised portion  232  produces a temporary near-quench region only when the piston  200  is near top dead center, subsequent combustion when the piston is on its down stroke allows efficient removal of unburned hydrocarbons in this region of the chamber. The combustion chamber  215  creates efficient removal of unburned hydrocarbons from portion  232 , because portion  232  is a significant fraction of the overall squish area (portion  232  plus portion  237 ), thus, overall emissions of unburned hydrocarbons from the combustion chamber  215  will be lower than those of a conventional combustion chamber. 
     By controlling the peak pressure and temperature used in high BMEP applications, advanced ignition timing can be utilized, thus, the life of the ignition plug  260  can be extended. High BMEP applications produce relatively high temperature and pressure in the combustion chamber  215 . Because the peak temperature and pressure can be controlled through the current chamber designs, the plug  260  can be ignited at a lower pressure (advanced ignition timing) than in conventional combustion chambers. Because the ignition plug  260  can be fired at lower pressure, the plug has a longer life span. The ignition plug  260  described herein can be any ignition plug that is capable of igniting the mixture. 
     The secondary chamber  235  is ignited as the flames from the primary combustion event travel across the inner annular raised portion  232 . The flames will combust the remaining mixture in the secondary chamber  235 . By providing the secondary chamber  235  with a predetermined volume of mixture, again, the peak temperature and pressure in the combustion chamber  215  can be controlled. By providing another chamber wall  239  and the outer annular raised portion  237 , the flame propagation speed can again be controlled and decrease the potential for knock. The flame propagation speed is slowed because the flame must travel up the wall  239  of the secondary chamber  235  and across the outer annular raised portion  237  to reach the inner wall  212  of the cylinder  210 . Again, the quenching area of outer portion  237  is constructed and designed to slow the flame propagation speed, but not quench the flame completely. Additionally, because the quenching region of the outer annular raised portion  237  is smaller (less area for heat loss transfer) than conventional quenching regions, the flames can reach the inner wall  212  of the cylinder  210  to combust any remaining mixture trapped in the outer portion  237 . At this time, the piston  200  descends after top dead center during the compression stroke. The cycle continues as described above. 
     The designs of the chambers  230 ,  235  can also influence the turbulence produced in the chambers  230 ,  235  and hence, the flame&#39;s propagation speed. The widths of the main chamber  230  and the secondary chamber  235  can be designed to help control the turbulence produced in the chambers. By narrowing the widths of the chambers  230 ,  235 , the turbulence generated within the respective chambers can increase. When the squish produced by the squish regions of the outer and inner annular raised portions  232 ,  237  enters the respective chambers  230 ,  235 , the turbulence and the flame propagation speed can increase leading to better combustion of the mixture. Although, turbulence leads to better mixing of the mixture, higher combustion efficiency temperature, and better combustion efficiency, it also increases propagation speed of the flames. As shown above, the increased temperature leads to increase NO x  productions, and the increased flame propagation speed leads to increase knock. The main chamber  230  and secondary chamber  235  are designed to increase turbulence to a predetermined point so that flame temperature and propagation speed will be controlled and prevent unnecessary production of NO x  and knock. 
     FIG. 3 is a perspective view of one embodiment of the piston  200 . The piston  200  includes a crown  207  having a main chamber  230 , preferably a circular recess, that is formed in the center thereof. The main chamber  230  has a wall  234  that defines the chamber. Also shown is a secondary chamber  235 , preferably an annular recessed groove, that is formed in the crown  207  of the piston  200 . The main chamber  230  and the secondary chamber  235  may be concentric about a central axis of the piston  200 . The secondary chamber  235  is separated from the main chamber  230  by an inner annular raised portion  232 . An outer annular raised portion  237  separates the outside wall  239  of the secondary chamber  235  and a perimeter of the piston&#39;s crown  207 . 
     In an alternative embodiment, the cylinder head  417  may have a main chamber  430  and a secondary chamber  435  on a base surface. FIG. 4 is a cross-sectional view an alternative power cylinder assembly  500 . The power cylinder assembly  500  comprises a cylinder head  417  having an ignition plug  460  that is disposed over a main chamber  430 , and a partition  432  that separates a secondary chamber  435  from the main chamber  430 . The power cylinder assembly  500  may further include a piston  400  having a crown  407 . The piston  400  may be slidably disposed in the cylinder  410  and may include annular grooves  422  around its outer surface  424 . The annular grooves  422  house one or more compression seals  420 . Additionally, the piston  400  may include an aperture  405  for connecting the piston to a connecting rod (not shown). In this embodiment, the piston&#39;s top surface  440  may not contain any chambers thereon. 
     Although the cylinder head  417  preferably includes the intake valve, the intake manifold, the exhaust valve, and the exhaust manifold, they are not shown in FIG. 4 for clarity. The cylinder head  417  can include a chamber that is divided into the main chamber  430  and the secondary chamber  435  by the partition  432 . Additionally, the combustion chamber  415  can be defined by the crown  407 , the inner wall  412  of cylinder  410 , the cylinder head  417  that includes chambers  430 ,  435  and the partition  432 . The partition  432  may be generally rectangular, but may be any shape or size and may include (depending on the design) wall  434  on a first surface, wall  436  on a second surface, wall  439  on a third surface, wall  465  on a fourth surface, and wall  466  on a fifth surface (see FIGS. 5 a - 5   d ). The partition  432  can be constructed and arranged to function as a flame control portion or quenching portion, and directs the flame when it travels from one chamber to another. By providing the partition  432  and directing the flame along the partition, heat loss to the walls of the cylinder head  417  and the partition can occur, thereby slowing the flame propagation speed. 
     FIGS. 5 a-d  show various embodiments of the configuration of the cylinder head  417  along line  5   a — 5   a  of FIG.  4 . In FIG. 5 a , the partition  432  preferably divides a chamber into the first and second and the second chamber  430 ,  435 , which generally can be half-moon shaped chambers of approximately equal size. The partition  432  may be constructed and arranged to direct the flames to travel along wall  436  (see FIG. 4) of the partition in order to travel from one chamber to another. 
     FIG. 5 b  shows another embodiment of a configuration of the cylinder head  417 . In this embodiment, the partition  432  is disposed in a chamber in the cylinder head  417  and divides the chamber into approximately two equal chambers, namely, a main chamber  430  and a secondary chamber  435 . Additionally, the partition  432  may be constructed and arranged so that the flames can travel along walls  465  and/or  466 , and preferably not wall  436  (FIG. 5 a ) in order to travel from one chamber to another. 
     FIG. 5 c  shows another embodiment of a configuration of the cylinder head  417 . In this embodiment, the partition  432  extends at least partially into a chamber, thereby dividing it generally into a main chamber  430  and a secondary chamber  435 . Additionally, the partition  432  may be constructed and arranged so that the flame can travel along wall  466 , and preferably not walls  436  and  465  in order to travel from one chamber to another. 
     FIG. 5 d  shows another embodiment of a configuration of the cylinder head  417 . In this embodiment, partition  432  is generally elliptical in shape, and divides a chamber in the cylinder head  417  generally into a main chamber  430  and a secondary chamber  435 . Additionally, the partition  432  may be constructed and arranged so that the flames can travel along walls  465  and  466  and preferably not wall  436  (See FIG. 4) in order to travel from one chamber to another. 
     In operation, a mixture is provided to combustion chamber  415  through the intake valve (not shown). The mixture may be separated into the main chamber  430  and the secondary chamber  435  when the piston  400  is at top dead center. The plug  460  ignites the mixture in main chamber  430  which produces combustion flames. Because the main chamber  430  has a defined volume of mixture than can burn at this point, the combustion pressure and temperature can be controlled and leads to low production of NO x . Additionally, in one embodiment, the flame propagation speed can be controlled by the slope or contour of wall  434  and the partition  432 . The flames can travel across the wall  434  of the main chamber  430 , across the wall  436  of partition  432  in order to combust the mixture in the secondary chamber  435 . In another embodiment, the flames can travel from main chamber  430  to secondary chamber  435  by crossing wall  465  and/or wall  466  of the partition  432 . In still another embodiment, the flame can travel from main the chamber  430  to the secondary chamber  435  by crossing the wall  466  of partition  432 . Regardless of which walls of the partition  432  that the flames travel across, each of the walls, including the wall of the cylinder head  217 , act as a quenching region in order to slow the flame propagation speed, reduce the potential for knock, and lead to more efficient combustion of the mixture. After the flames cross the partition  432 , it can ignite the mixture in secondary chamber  435 . Because the secondary chamber  435  also has a defined volume of mixture that can burn at this point, the combustion pressure and temperature can be controlled leading to low production of NO x . 
     The embodiments of the invention provide a controlled combustion process by a cascaded combustion event within each segregated chamber. Although the main chamber is preferably a circular recess and the secondary chamber is preferably an annular recessed groove as described above, in other embodiments, the main chamber may be an annular recessed groove and the secondary chamber may be a circular recess. Additionally, one skilled in the art will also recognize that the chambers may include only circular recesses or only annular recessed grooves or any combinations thereof, as shown in FIGS. 6 and 7. Although only two chambers are mainly discussed herein, the invention may be used with multiple chambers of varying sizes, shapes, volumes, having a lower portion being concave and other characteristics. Also, the embodiments discussed above may be used on either the crown of the piston or on the cylinder head or a combination thereof. The chambers may be constructed to have varying widths to control turbulence therethrough. Also, the length and area of the squish/quenching regions may be adjusted to control the flame propagation speed. Additionally, the invention may be used with any combustion engine including two and four stroke engines. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.