Patent Publication Number: US-7909271-B2

Title: Fuel injector nozzle for an internal combustion engine

Description:
This application is a divisional of U.S. patent application Ser. No. 11/802,289, filed May 22, 2007, now U.S. Pat. No. 7,444,980 which is a divisional of U.S. patent application Ser. No. 11/353,998, filed Feb. 15, 2006, now U.S. Pat. No. 7,290,520, which is a divisional of U.S. patent application Ser. No. 10/448,063, filed May 30, 2003 now U.S. Pat. No. 7,032,566, each of which is incorporated herein by reference in its entirety. 
    
    
     U.S. GOVERNMENT RIGHTS 
     The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of Contract Nos. DE-FC05-00OR22806 and DE-FC05-97OR22605 awarded by the Department of Energy. 
    
    
     TECHNICAL FIELD 
     This invention relates generally to fuel systems for internal combustion engines, and more particularly to nozzle configurations of fuel injectors of fuel systems of internal combustion engines. 
     BACKGROUND 
     The conventional combustion process in diesel engines is initiated by the direct injection of fuel into a combustion chamber containing compressed air. The fuel is almost instantaneously ignited upon injection into the highly compressed combustion chamber, and thus produces a diffusion flame or flame front extending along the plumes of the injected fuel. The fuel is directly injected into the combustion chamber by a fuel injector having a nozzle tip extending into the combustion chamber. For example, the nozzle tip may extend slightly into the combustion chamber from a wall of the chamber located opposite a reciprocating piston of the combustion chamber. 
     More demanding emissions standards have necessitated attempts at reducing smoke and NOx byproducts of the combustion process, while maintaining or improving fuel efficiency. One approach to meeting the difficult emissions standards includes incorporating what has been referred to as a Homogeneous Charge Compression Ignition (HCCI) process into the engine cycle. The HCCI process may be more accurately referred to as a controlled auto-ignition process. Such a process operates by injecting fuel into the combustion chamber prior to the point at which the combustion chamber reaches a pressure sufficient to auto-ignite the fuel. Such a fuel injection timing allows for compression of a diluted mixture of air and fuel until auto-ignition occurs. This controlled auto-ignition process provides a combustion reaction volumetrically within the engine cylinder as the combustion chamber volume is reduced by the piston. This type of combustion avoids localized high temperature regions associated with the flame fronts, and thereby reduces smoke and NOx byproducts of the combustion. 
     Conventional fuel injectors used for injecting fuel into highly pressurized or relatively lower pressurized combustion chambers include a nozzle tip having a plurality of passages allowing fuel from the injector to be injected into the combustion chamber. The number, size, and orientation of the passages in the nozzle tip affect the production of smoke, production of NOx, and fuel efficiency associated with the combustion. 
     U.S. Pat. No. 4,919,093 to Hiraki et al. discloses a direct injection type diesel engine having a fuel injector nozzle tip including a plurality of injection holes arranged in two rows concentrically relative to a longitudinal axis of the injector nozzle. The injection holes of the two rows are disclosed as forming a zigzag pattern. Accordingly, as disclosed in the illustrated embodiments, each of the two rows include the same number of injection holes. Further, Hiraki et al. discloses that the distal-most row of holes form an acute angle of 45° or greater with the longitudinal axis of the injector nozzle. 
     The number, size, and orientations of the holes of the fuel injector nozzle tip of Hiraki et al. provide a narrow range or diffusion of fuel plumes into the combustion chamber. This is evidenced by the fact that the injector holes of the distal-most row of the nozzle tip are orientated to form an arc of 90° between opposing nozzle holes of the row. Accordingly, a majority of the area within the combustion chamber formed by the 90° arc does not directly receive injected fuel. Such a narrow range of diffusion of fuel plumes limits the mixing of the fuel with the air, thus increasing the localized high temperature regions in the combustion chamber and thereby producing unwanted smoke and NOx. 
     The present invention provides a fuel system for an internal combustion engine that avoids some or all of the aforesaid shortcomings in the prior art. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the invention, a direct injection fuel injector nozzle tip includes an outer nozzle tip surface portion, and an inner nozzle tip surface portion. A plurality of passages allow fluid communication between the inner nozzle tip surface portion and the outer nozzle tip surface portion and directly into a combustion chamber of an internal combustion engine. Each of the plurality of passages has an inner surface aperture on the inner nozzle tip surface portion and an outer surface aperture on the outer nozzle tip surface portion. A first group of the passages have inner surface apertures located in a first common plane. A second group of the passages have inner surface apertures located in at least a second common plane substantially parallel to the first common plane, and the second group having more passages than the first group. 
     According to another aspect of the present invention, a direct injection fuel injector nozzle tip includes an outer nozzle tip surface portion, and an inner nozzle tip surface portion. A plurality of passages allow fluid communication between the inner nozzle tip surface portion and the outer nozzle tip surface portion and directly into a combustion chamber of an internal combustion engine. Each of the plurality of passages has an inner surface aperture on the inner nozzle tip surface portion and an outer surface aperture on the outer nozzle tip surface portion. A first group of passages have inner surface apertures located in a first common plane. A second group of passages have inner surface apertures located in at least a second common plane substantially parallel to the first common plane. The first group of passages each have a longitudinal axis extending at acute angles alpha (α) of 55 degrees or greater from the first common plane, the acute angles alpha (α) being measured in a plane perpendicular to the first common plane. The second group of passages each have a longitudinal axis extending at acute angles theta (θ) of 27.5 degrees or greater from the second common plane, the acute angles theta (θ) being measured in a plane perpendicular to the second common plane. 
     According to yet another aspect of the present invention, a method of providing combustion within a combustion chamber of an internal combustion engine includes providing air into the combustion chamber and injecting fuel into the combustion chamber through a plurality of passages located in a nozzle tip of a fuel injector so as to form a plurality of fuel plumes in the combustion chamber. Each of the plurality of fuel plumes corresponds to one of the plurality of passages and shares a common axis with the corresponding opening. The axis of each passage extends into a piston of the combustion chamber at a piston position of 30 degrees before top dead center. The method further includes compressing the air and fuel in the combustion chamber to auto-ignite the mixture. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a combustion chamber assembly of a internal combustion engine according to the disclosure; 
         FIG. 2  is an enlarged cross-sectional view of the fuel injector nozzle tip of  FIG. 1 ; 
         FIG. 3  is an enlarged internal view of the nozzle tip of  FIG. 2 ; 
         FIG. 4  is an enlarged cross-sectional view of an alternative fuel injector nozzle tip according to the disclosure; 
         FIG. 5  is an enlarged internal view of the nozzle tip of  FIG. 4 ; 
         FIG. 6  is a schematic illustration of fuel plumes provided by the nozzle tip of  FIGS. 2 and 3 ; and 
         FIG. 7  is a schematic illustration of a cross-sectional end view of the fuel plumes illustrated in  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 1  illustrates a combustion chamber assembly of an internal combustion engine including a combustion chamber  10 . Such an engine may include, for example, a four stroke diesel fuel powered engine. The combustion chamber  10  is formed by a cylinder sidewall  12 , a cylinder end wall  14 , and a reciprocating piston  16 , and includes a combustion chamber longitudinal axis  17 . The piston  16  may have a top surface  18  forming a piston crater  20 . As is conventional in the art, an intake port  22 , intake valve  24 , exhaust port  26 , and exhaust valve  28  may be located about the cylinder end wall  14 . 
     A fuel injector  30  may include a nozzle tip  32  extending directly into the combustion chamber  10  through an opening  33  in the cylinder end wall  14 . The fuel injector  30  may be concentric or parallel with the longitudinal axis  17  of the combustion chamber  10  ( FIG. 1 ), or may extend at an acute angle with respect to the longitudinal axis  17  of the combustion chamber. Further, the fuel injector  30  may be of any conventional type. For example, the fuel injector  30  may be of the mechanically actuated, hydraulically actuated, or common fuel type, and may be designed for single mode or mixed mode operations. 
       FIG. 2  illustrates an enlarged cross-sectional view of the fuel injector nozzle tip  32  of  FIG. 1 . The nozzle tip  32  may include an internal valve receiving opening  34  having a tapering valve seat section  36  extending to a distally located tip sac  38 . Tip sac  38  may be formed in a substantially concave shape and include an inner surface  40  and an outer surface  42 . Tip sac  38  may also include a plurality of passages  44  extending from an inner surface aperture  45  on the inner surface  40  to an outer surface aperture  47  on the outer surface  42  of the tip sac  38 . It is understood that nozzle tip  32  may also be formed as a valve closed orifice type nozzle tip, wherein passages  44  are located outside the tip sac  38 . Passages  44  may have a substantially constant diameter between their inner surface apertures  45  and their outer surface apertures  47 , as shown in  FIG. 2 . Alternatively, passages  44  may include other configurations such as, for example, a curved or straight taper with a larger diameter at the outer or inner surface apertures ( 45 ,  47 ), radiusing located at either or both of the outer and inner surface apertures ( 45 ,  47 ), or counterbores located at either or both of the outer and inner surface apertures ( 45 ,  47 ). 
       FIG. 3  illustrates an internal view of the nozzle tip  32  of  FIG. 2 . As illustrated, tip sac  38  may include a total of twenty four (24) passages  44 , with three groups of eight (8) passages  44  forming three different rings  46 ,  48 ,  50  about the inner surface  40  of tip sac  38 . The inner ring  46  of passages  44  will be hereinafter referred to as the distal ring  46 , the second ring  48  of passages  44  will hereinafter be referred to as the intermediate ring  48 , and the outer ring  50  of passages  44  will hereinafter be referred to as the proximal ring  50 . As illustrated in  FIG. 3 , the rings ( 46 ,  48 ,  50 ) formed in the inner surface  40  of the tip sac  38  each have inner surface apertures  45  lying in, or lying substantially in, a common plane. These three different common planes of rings  46 ,  48 , and  50  will be hereafter identified as distal common plane  49 , intermediate common plane  51  and proximal common plane  53 , and are shown in  FIG. 2 . The distal, intermediate and proximal common planes  49 ,  51 ,  53  are substantially parallel to one another and substantially perpendicular to the longitudinal axis  17  of the combustion chamber  10 . As stated herein, the phrase “lying in a common plane” or “located in a common plane” includes a ring ( 46 ,  48 ,  50 ) configured so that a plane extends through any portion of each of the inner surface apertures  45  of passages  44  forming the particular ring ( 46 ,  48 ,  50 ). It is understood that a fuel injector orientated at an acute angle with respect to the longitudinal axis  17  of the combustion chamber  10  will still have passages  44  forming common planes  49 ,  51 ,  53  lying substantially perpendicular to the longitudinal axis  17  of the combustion chamber  10 . 
     The intermediate ring  48  of passages  44  may be arranged closer to the proximal ring  50  than the distal ring  46 . Alternatively, intermediate ring  48  and proximal ring  50  may be combined to form a single ring of passages  44 , with each opening  44  in the single ring located in substantially a common plane. As shown in  FIG. 3 , intermediate ring  48  and proximal ring  50  each include eight (8) passages  44  together totaling twice the number of passages  44  of the distal the ring  46 . Accordingly, a nozzle tip  32  according to the present disclosure may include an intermediate ring  48  and proximal ring  50  together totaling at least twice the number of passages  44  of the distal ring  46 . 
     Referring again to  FIG. 2 , the passages  44  of the distal ring  46  each have a longitudinal axis  54  at acute angles alpha (α) from the distal common plane  49 . The passages  44  of intermediate ring  48  each have longitudinal axes  56  at acute angles theta (θ) from the intermediate common plane  51 . Further, the passages  44  of proximal ring  50  each have a longitudinal axis  58  at acute angles beta (β) from the proximal common plane  53 . The acute angles for alpha (α), theta (θ) and beta (β) are measured in a plane that is perpendicular to the common planes  49 ,  51 ,  53 . The acute angles for alpha (α), theta (θ) and beta (β) may be as follows:
         alpha (α)˜≧55°   theta (θ)˜≧27.5°   beta (β)˜≧27.5°       

     For example, the nozzle tip  32  of  FIG. 2  may include acute angles alpha (α) equal to approximately 55° from the distal common plane  49 , and acute angles theta (θ) and beta (β) equal to approximately 27.5° from the intermediate and proximal common planes  49 ,  51 . Further, the nozzle tip  32  of  FIG. 2  may include acute angles alpha (α) equal to or greater than approximately 65° from the distal common plane  49 , and acute angles theta (θ) and beta (β) equal to or greater than approximately 45° from the intermediate and proximal common planes  49 ,  51 . Even further, nozzle tip  32  may include the passages  44  of distal ring  46  all at a substantially common acute angle alpha (α) equal to approximately 65° from the distal common plane  49 , and passages  44  of the intermediate ring  48  and proximal ring  50  all at approximately the same acute angle theta (θ) and beta (β) equal to approximately 45° from the intermediate and proximal common planes  49 ,  51 . It is understood, however, that passages  44  forming an individual ring ( 46 ,  48 ,  50 ) do not all have to be oriented at the same acute angle. 
     Even further nozzle tip arrangements may be contemplated by this disclosure. For example, a nozzle tip  32  may include a total of twenty four (24) passages  44  with a substantially common acute angle alpha (α) equal to or greater than approximately 60° from the distal common plane  49 , and a substantially common acute angle theta (θ) and beta (β) equal to or greater than approximately 37.5° from the intermediate and proximal common planes  51 ,  53 . Even further, a nozzle tip having a total of twenty four (24) passages  44  may have an acute angle alpha (α) equal to or greater than approximately 55° from the distal common plane  49 , and an acute angle theta (θ) and beta (β) equal to or greater than approximately 27.5° from the intermediate and proximal common planes  51 ,  53 . 
     Acute angles theta (θ) and beta (β) may extend at the same or different acute angles from respective intermediate and proximal common planes  51 ,  53 . For example, an arrangement of passages  44  according to this disclosure may include acute angles of alpha (α) equal to approximately 82.5°, theta (θ) equal to approximately 67.5° and beta (β) equal to approximately 52.5°. Further, each ring ( 46 ,  48 ,  50 ) of passages  44  may be formed with substantially the same diameter and shape, or the rings may have passages  44  of a different diameter and/or shape than passages  44  of another ring. For example, each of the passages  44  of the nozzle tip  32  of  FIG. 2  may have a diameter of approximately 0.105 mm (0.0041 inches). 
       FIGS. 4 and 5  illustrate an alternative injector nozzle tip  60  according to the present disclosure. Nozzle tip  60  includes a plurality of passages  62  extending through the nozzle tip  60 . Similar to the passages  44  discussed above with respect to  FIGS. 2 and 3 , inner surface apertures  63  of passages  62  of the nozzle tip  60  of  FIGS. 4 and 5  form a distal ring  66 , an intermediate ring  68  and a proximal ring  70  ( FIG. 5 ) and may be substantially cylindrical or tapered in shape. Again, similar to the nozzle tip  32 , passages  62  of each individual ring ( 66 ,  68 ,  70 ) lie in, or substantially lie in, a common plane, with each common plane. These three different common planes  67 ,  69  and  71  are substantially parallel to one another and are shown in  FIG. 4 . 
     Each of the passages  62  of the distal ring  66 , intermediate ring  68  and proximal ring  70  have a longitudinal axis  72 ,  74  and  76 , respectively ( FIG. 4 ). In contrast to nozzle tip  32  of  FIGS. 2 and 3 , the rings ( 66 ,  68 ,  70 ) of nozzle tip  60  are substantially equally spaced from one another. Further, nozzle tip  60  includes a total of thirty two (32) passages  62 , with six (6) passages  62  in the distal ring  66 , ten (10) passages  62  in the intermediate ring  68 , and sixteen (16) passages  62  in the proximal ring  70 . Similar to the nozzle tip  32  of  FIGS. 2 and 3 , the intermediate and proximal rings  68 ,  70  of nozzle tip  60  together have passages  62  totaling at least twice as many passages  62  as the distal ring  66  of the nozzle tip  60 . 
     Referring to  FIG. 4 , the passages  62  of the distal ring  66  are at acute angles alpha 1  (α 1 ) from the distal common plane  67 , passages  62  of the intermediate ring  68  are at acute angles theta 1  (θ 1 ) from the intermediate common plane  69 , and the passages  62  of proximal ring  70  are at acute angles beta 1  (β 1 ) from the proximal common plane  71 . As noted above with respect to the angle measurements for nozzle tip  32 , acute angles for alpha 1  (α 1 ), theta, (θ 1 ) and beta, (β 1 ) are measured in a plane that is perpendicular to the common planes ( 67 ,  69 ,  71 ). The acute angles for alpha 1  (α 1 ), theta, (θ 1 ) and beta, (β 1 ) may be as follows:
         alpha 1  (α 1 )˜≧75°   theta 1  (θ 1 )˜≧60°   beta 1  (β 1 )˜≧45°       

     For example, the nozzle tip  60  of  FIG. 4  may include passages  62  at a substantially common acute angle alpha 1  (α 1 ) equal to approximately 75° from the distal common plane  67 , passages  62  at a substantially common acute angle theta 1  (θ 1 ) equal to approximately 60° from the intermediate common plane  69 , and passages  62  at a substantially common acute angle beta 1  (β 1 ) equal to approximately 45° from the proximal common plane  71 . Passages  62  forming an individual ring ( 66 ,  68  and  70 ) do not all have to be oriented at the same acute angle. 
     Each ring ( 66 ,  68 ,  70 ) of passages  62  of the nozzle tip  60  may be formed with substantially the same diameter and shape, or the rings may have passages  62  of a different diameter and/or shape than passages  62  of another ring. For example, each of the passages  62  of  FIG. 4  may have a diameter of approximately 0.075 mm (0.0029 inches). 
     INDUSTRIAL APPLICABILITY 
     Reference will now be made to the operation of the nozzle tip  32  ( FIG. 2  and  FIG. 3 ) of the combustion chamber  10  of an internal combustion engine according to the present disclosure. The nozzle tip  32  associated with this exemplary operational description includes passages  44  having a substantially common acute angle alpha (α) equal to approximately 65° from the distal common plane  49 , and a substantially common acute angle theta (θ) and beta (β) equal to approximately 45° from the intermediate and proximal common planes  51 ,  53 . Further, the operation will be described in connection with a controlled auto-ignition or HCCI technique, but it is understood that the nozzle tips of the present disclosure may be utilized in conventional high compression injection techniques as well. 
     Referring to  FIG. 4 , the auto-ignition technique includes the steps of providing air into the combustion chamber  10 , injecting fuel into the combustion chamber  10  through the plurality of passages  44  located in the nozzle tip  32  of the fuel injector  30  so as to form a plurality of fuel plumes  78  in the combustion chamber  10 , and compressing the air and fuel in the combustion chamber  10  to auto-ignite the mixture. The injecting step may be initiated prior to a piston position of approximately 70 degrees before top dead center and the injection step occurs only once per cycle of the piston  16 . It is understood that other gases may be provided to the combustion chamber  10 , for example exhaust gases may be present by way of an exhaust gas recirculation (EGR) system. 
       FIG. 6  illustrates the compression stroke of piston  16  at a piston position of 50° before top dead center (BTDC). At this point in the combustion cycle, intake air has entered the combustion chamber  10  and is being compressed and mixed with fuel injected from nozzle tip  32 . As noted above, other gases may exist in combustion chamber  10 , for example exhaust gases may be present by way of an exhaust gas recirculation (EGR) system. The injected fuel, for example diesel fuel, forms fuel plumes  78  within the combustion chamber  10 . As the piston  16  progresses toward top dead center, the air/fuel mixture is compressed and eventually auto-ignites when the pressure in the combustion chamber  10  exceeds a threshold auto-ignition pressure of the mixture. The fuel plumes  78  according to this arrangement of passages  44  provide completely or substantially completely developed fuel plumes  78  when the piston is at a position of approximately 50° BTDC. These completely or substantially completely developed fuel plumes  78  are near but are not substantially in contact with the cylinder sidewall  12  when the piston is at a position of approximately 50° BTDC. It is noted that the fuel injector  30  having this nozzle tip arrangement may be initiated when the piston is approximately 90° BTDC. As understood in this disclosure, initiation of the fuel injector  30  corresponds to the sending of an electrical signal energizing the fuel injector for fuel injection, or the beginning of a mechanical actuation of the fuel injector  30  associated with injecting fuel from the fuel injector  30 . 
       FIG. 6  illustrates the fuel plumes  78  in a completely or substantially completely developed state. The minimal contact with the cylinder sidewall  12  is based on the fact that the fuel plumes  78  each generally follow the longitudinal axes ( 54 ,  56 ,  58 ) of their corresponding passage  44 . As shown in dotted lines in  FIG. 6 , the longitudinal axes  54 ,  56  and  58  all extend into the piston crater  20  when the piston  16  is at a piston position of 50° BTDC. Such an arrangement provides fuel plumes  78  that do not, or only minimally, contact the cylinder sidewall  12  of combustion chamber  10 . Further, the injector passages  44  also provide for individual fuel plumes  78  that do not substantially overlap or intersect one another. This aspect of the fuel plumes  78  is illustrated in  FIG. 7 , which shows an end view cross-section of the fuel plumes  78  provided by the nozzle tip  32 . 
     In addition to providing substantially completely developed, non-overlapping, fuel plumes  78  minimally contacting the cylinder sidewall  12 , passages  44  in nozzle tip  32  also provide for a highly homogenous mixture of fuel within the combustion chamber  10 . When used in a controlled auto-ignition or HCCI type combustion technique, the highly homogenous mixture provides reduced smoke exhaust, reduced NOx, and a reduction in unburned hydrocarbons resulting in improved emissions and better fuel economy. Even when used in a non-HCCI direct injection technique, the passages  44  of nozzle tip  32  reduce the formation of detrimental high temperature regions within the combustion chamber  10 . 
     Nozzle tip  60  provides for fuel plumes similar to those of nozzle tip  32 , except that angle differences between theta 1  (θ 1 ) and beta 1  (β 1 ) create a third ring of fuel plumes. Fuel plumes provided by nozzle tip  60  having an acute angle alpha 1  (α 1 ) equal to approximately 75°, an acute angle theta 1  (θ 1 ) equal to approximately 60° and an acute angle beta 1  (β 1 ) equal to approximately 45° are completely or substantially completely developed when the piston  16  is located approximately 50° BTDC. These completely or substantially completely developed fuel plumes are adjacent but not substantially in contact with the cylinder sidewall  12  when the piston  16  is located approximately 50° BTDC. Further, the longitudinal axes of the passages  44  formed by nozzle tip  60  do not initially intersect the cylinder wall  12 , but rather extend into the piston crater  20  when the piston  16  is approximately 50° BTDC. It is noted that the fuel injector having this nozzle tip  60  may be initiated when the piston  16  is at a position of approximately 90° BTDC. 
     Even further, nozzle tip  32  described above with acute angles alpha (α) equal to or greater than approximately 60° from the distal common plane  49  and a substantially common acute angle theta (θ) and beta (β) equal to or greater than approximately 37.5° from the intermediate and proximal common planes  51 ,  53  may provide substantially completely developed fuel plumes when the piston  16  is at a position of approximately 40° BTDC. When the longitudinal axes of passages  44  are arranged at such acute angles they do not initially intersect the cylinder sidewall  12 , but rather extend into the piston crater  20  when the piston  16  is at a position of approximately 40° BTDC. The fuel injector  30  having this nozzle tip may be initiated when the piston is at a position of approximately 80° BTDC. 
     Finally, the above described nozzle tip having acute angles alpha (α) equal to or greater than approximately 55° and an acute angle theta (θ) and beta (β) equal to or greater than approximately 27.5° may provide substantially completely developed fuel plumes when the piston  16  is at a position of approximately 30° BTDC. When the longitudinal axes of passages  44  are arranged at such angles they do not initially intersect the cylinder sidewall  12 , but rather extend into the piston crater  20  when the piston  16  is at a position of approximately 30° BTDC. The fuel injector  30  with this nozzle tip arrangement may be initiated when the piston is at a position of approximately 70° BTDC. 
     Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the invention being indicated by the following claims.