Patent Application
20160298528
The present disclosure generally relates to internal combustion engines and, more particularly, relates to ducted combustion systems for internal combustion engines.
Modern combustion engines may include one or more cylinders as part of the engine. The cylinder and an associated piston may define a combustion chamber therebetween. Within the combustion chamber, fuel for combustion is directly injected into the combustion chamber by, for example, a fuel injector, which is associated with the cylinder and has an orifice disposed such that it can directly inject fuel into the combustion chamber.
Different mixtures and/or equivalence ratios of the fuel/air mixture within the fuel jet may produce different results during combustion. The manners in which the injected fuel mixes and/or interacts with the air and other environmental elements of the combustion chamber may impact combustion processes and associated emissions. Further, if the fuel and air mixing is inadequate, then suboptimal or abnormally large amounts of soot may form within the combustion chamber.
To aid in preventing or reducing soot formation and to increase efficiency in such combustion engines, systems and methods for ducted combustion have been developed. For example, U.S. Patent Publication No. 2012/0186555 (“Ducted Combustion Chamber for Direct Injection Engines and Method”) discloses ducted combustion within a combustion engine. The ducts of the '555 application generally include fins disposed around a fuel jet injected by a fuel injector. Such ducts may form a passageway corresponding to an orifice of the fuel injector, into which fuel jets are injected. The fuel jets may be channeled into the ducts, which may improve fuel combustion because upstream regions of a direct-injected fuel jet may be affected by faster and more uniform mixing as well as by an inhibition or reduction of entrainment of combustion products from downstream regions of the same or neighboring jets.
While the teachings of the '555 application are advantageous in providing an improved fuel/air mixture, further improvements in fuel/air mixtures are always desired, as such improvements may further reduce emissions and soot formation. Therefore, systems and methods for ducted combustion that utilize duct structures, defining a plurality of curved ducts, for improving fuel/air mixtures are desired.
In accordance with one aspect of the disclosure, a ducted combustion system is disclosed. The ducted combustion system may include a combustion chamber, which is defined as an enclosure bound at a first end by a flame deck surface of a cylinder head of an internal combustion engine and bound at a second end by a piston top surface of a piston disposed within the internal combustion engine. The system may further include a fuel injector in fluid connection with the combustion chamber and including a plurality of orifices in an injector tip of the fuel injector, the plurality of orifices injecting fuel into the combustion chamber as one or more fuel jets. The system may further include a duct structure defining a plurality of curved ducts and disposed within the combustion chamber between the flame deck surface and the piston top surface, the plurality of ducts being disposed such that each of the plurality of orifices inject each of the plurality of fuel jets, at least partially, into one of the plurality of curved ducts.
In accordance with another aspect of the disclosure, an internal combustion engine is disclosed. The internal combustion engine may include an engine block having at least one cylinder bore. The internal combustion engine may further include a cylinder head having a flame deck surface disposed at one end of the cylinder bore. The internal combustion engine may further include a piston connected to a crankshaft and configured to reciprocate within the cylinder bore, the piston having a piston top surface facing the flame deck surface such that a combustion chamber is defined within the cylinder bore bound at a first end by the flame deck surface and at a second end by the piston top surface. The internal combustion engine may further include a fuel injector in fluid connection with the combustion chamber and including a plurality of orifices in an injector tip of the fuel injector, the plurality of orifices injecting fuel into the combustion chamber as one or more fuel jets. The internal combustion engine may further include a duct structure defining a plurality of curved ducts and disposed within the combustion chamber between the flame deck surface and the piston top surface, the plurality of ducts being disposed such that each of the plurality of orifices inject each of the plurality of fuel jets, at least partially, into one of the plurality of curved ducts.
In accordance with yet another aspect of the disclosure, a method for operating a combustion system is disclosed. The method may include injecting a plurality of fuel jets into a combustion chamber of an internal combustion engine, the combustion chamber defined as an enclosure bound at a first end by a flame deck of a cylinder of an internal combustion engine, and bound at a second end by a piston top surface of a piston disposed within the internal combustion engine. The method may further include directing the plurality of fuel jets, at least partially, into respective members of a plurality of curved ducts, each of the plurality of curved ducts being defined within a duct structure, to provide a substantially uniform mixture of fuel and air within the combustion chamber.
Other features and advantages of the disclosed systems and principles will become apparent from reading the following detailed disclosure in conjunction with the included drawing figures.
While the following detailed description will be given with respect to certain illustrative embodiments, it should be understood that the drawings are not necessarily to scale and the disclosed embodiments are sometimes illustrated diagrammatically and in partial views. In addition, in certain instances, details which are not necessary for an understanding of the disclosed subject matter or which render other details too difficult to perceive may have been omitted. It should therefore be understood that this disclosure is not limited to the particular embodiments disclosed and illustrated herein, but rather to a fair reading of the entire disclosure and claims, as well as any equivalents thereto.
Turning now to the drawings and with specific reference to
The combustion chamber 14 is shown in greater detail in the front, cross-sectional view of
During operation of the engine 10, air enters the combustion chamber 14 via one or more intake valves 34 (shown in
Within the combustion chamber 14, uniformity of the fuel/air mixture may be relevant to the combustion efficiency and may be relevant to the amount and type of combustion byproducts that are formed. For example, if the fuel/air mixture is too rich in fuel due to insufficient mixing within the combustion chamber 14, then higher soot emissions may occur within the fuel jets 35 and/or combustion efficiency may be affected. However, using a duct structure 40, which defines a plurality of curved ducts 45, disposed within the combustion chamber 14 may provide for more uniform fuel/air mixing within the fuel jets 35. Using such a duct structure 40, which defines a plurality of ducts 45, a lift-off length of a flame associated with a fuel jet 35 may be altered (extended or reduced) to achieve an optimized lift-off length. The duct structure 40 may alter lift-off length due to energy exchange between the duct structure 40 and the fuel/air mixture of the fuel jet 35, due to altering fluid dynamics of the fuel/air mixture of the fuel jet 35, and/or due to prevention of lift-off length recession by acting as a flame arrester.
The duct structure 40 may be disposed within a flame region 42 of the combustion chamber 14. The flame region 42 may be defined as a region of the combustion chamber 14 extending from the flame deck surface 16 to the piston top surface 22, when the piston 24 is at or close to a maximum compression distance or top dead center (TDC) position.
To further illustrate the duct structure 40 and its interaction with one or more fuel jets 35 injected from the one or more orifices 36 of the tip 32 of the fuel injector 30, the duct structure 40, within the combustion chamber 14, is shown in greater detail in
The curved ducts 45 may include a first portion 51 and a second portion 52. The first portion 51 may have an alignment that is substantially straight, meaning it may be substantially parallel with the direction of the cylinder in which it is disposed. The first portion 51 may include the opening 46 and, as such, the first portion 51 may be directly aligned with the orifice 36. When the fuel jet 35 is injected, it may directly enter the first portion 51 at the opening 46. Once the fuel jet passes through the first portion 51, it may enter the second portion 52 of the curved duct 45, the second portion being curved with respect to the first portion and allowing the fuel jet 35 to exit the duct structure 40 via the outlet 47. In an example embodiment, the second portion 52 may be curved in the range of 30-150 degrees with respect to the first portion 51, such an angle may be defined as an angle between the opening 46 and the outlet 47. However, other angles of curvature for the second portion 52 are certainly possible.
Use of the duct structure 40, having the plurality of curved ducts 45, may provide improved mixing of a fuel/air mixture within the fuel jets 35 prior to combustion. The duct structure 40 may direct combustion away from the fuel injector 30, such that longer flame lift-off lengths may be achieved. Further, by channeling the fuel jets 35 into the duct structure 40, entrainment of combustion products from downstream regions of the same or neighboring fuel jets 35 may be reduced or inhibited. By using such duct structures 40, levels of soot within the combustion chamber 14 may be reduced greatly.
While the example embodiment of
In some such examples, wherein the duct structure 40 is affixed to the piston 24, the duct structure 40 may be affixed to the piston top surface 22 via a spring 60, as shown in
The present disclosure relates generally to internal combustion engines and, more specifically, to ducted combustion systems. While the present disclosure shows the embodiments as related to internal combustion engines having reciprocating pistons, the teachings of the disclosure are certainly applicable to other combustion systems, which utilize diffusion or non-premixed flames, such as gas turbines, industrial burners, and the like. As discussed above, the various arrangements of ducts and their related elements are useful in promoting a substantially uniform fuel/air mixture within fuel jets and may inhibit or reduce entrainment of recirculated combustion products from downstream regions into upstream regions of fuel jets injected into combustion chambers. However, using such systems and methods for ducted combustion may also decrease fuel/air mixing, while reducing equivalence ratio at the lift-off length.
An example method utilizing the ducted combustion systems shown in
In some examples, the method 200 may include maintaining a substantially constant position for the duct structure 40 within the combustion chamber 14 when the piston 24 is in reciprocating motion, as shown in block 230. In such examples, said positioning may be accomplished by affixing the duct structure 40 to the piston 24 via a spring 60 that is configured to maintain such a constant position for the duct structure 40 within the combustion chamber 14 when the piston 24 is in reciprocating motion.
The disclosed ducted combustion systems may be configured to use duct structure 40 to direct combustion away from the fuel injector tip 32, so that the equivalence ratio at the flame lift-off length, produced during combustion. is reduced. Maintaining a reduced equivalence ratio at the lift-of length may reduce soot formation. Achieving a reduced equivalence ratio at the lift-off length may be accomplished by altering the lift-off length, when employing any of the aspects of the present application. Alterations to the lift-off length may occur if heat is transferred from the fuel/air mixture of the fuel jets 35 to the duct structure 40. Additionally or alternatively, alterations to the lift-off length may be achieved by alteration of fuel jet fluid dynamics, which are resultant of characteristics of the ducts 45. Further, use of ducts 45 may prevent lift-off length recession by acting as a flame arrester.
Substantially soot-free combustion may be achieved if the equivalence ratio at the flame lift-off length is less than two. Therefore, at block 240, the method 200 may include maintaining an equivalence ratio of less than 2 at the flame lift-off length.
At block 250, the method 200 may reduce entrainment of recirculated combustion products from a downstream region of the fuel jet 35 to an upstream region of the fuel jet 35 by substantially containing a segment of the fuel jet 35 within a curved duct 45. Reducing such entrainment may lead to an overall reduction in soot production within the combustion chamber 14 and may lead to greater overall efficiency of the internal combustion engine 10. Presence of ducts 45 may alter amount and position of entrainment of recirculated combustion products, within the fuel jets 35
It will be appreciated that the present disclosure provides ducted combustion systems, internal combustion engines utilizing ducted combustion, and methods for operating combustion systems utilizing ducted combustion. While only certain embodiments have been set forth, alternatives and modifications will be apparent from the above description to those skilled in the art. These and other alternatives are considered equivalents and within the spirit and scope of this disclosure and the appended claims.
