FIELD OF INVENTION:
The present subject matter described herein, relates to an exhaust port structure, and, in particular to, an exhaust port structure for enhancing mass flow rate efficiency in an internal combustion engine.
BACKGROUND AND PRIOR ART:
In general exhaust emission standards that require vehicle manufacturers to greatly reduce pollutants such as hydrocarbons (HC), oxides of nitrogen (NOx), and carbon monoxide (CO) emissions that may emanate from internal combustion engines. Although an operation of a number of combustion chamber devices are thought to be responsible for pollutants, it is generally thought that crevice volume fuel storage and release, via a vehicle's exhaust valves, plays a major role. The existing exhaust port is configured with side and top profile angles which are not optimized as per current mass production line such that the exhaust port flow can be detached due to high flow resistance. In this way the exhaust port is to be re-designed by performing the better in port mass flow and velocity.
[003] Fig. 1 illustrate general structure of exhaust port with combustion chamber. As shown in the figure 1, the exhaust port structure has an exhaust air passageway and a pair of first and second exhaust ports 101, 102 branching from the exhaust air passageway toward first and second exhaust valve openings 105, 106. Further, a first valve and a second valve 103, 104 are slidably arranged in the first and the second exhaust valve openings 105, 106 to open and close the first and the second exhaust valve openings 105, 106 allow passage burnt gases from the combustion chamber 107 to exhaust pipe that is connected with the exhaust passagway. Furthermore, stems 103a, 104a of the first valve and the second valve 103, 104 slides through stem guide portions in the exhaust port structure. The exhaust port structure has a throat portion that connects the first and the second exhaust port 101, 102 with the first and the second exhaust valve openings 105, 106.
[004] There is a need in the art to modify the structure and to optimize the parameters of the exhaust port structure to improve the scavenging of burnt gases to avoid knocking and pre-ignition and to reduce pumping loss.
OBJECTS OF THE INVENTION:
[005] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed hereinbelow.
[006] The principal objective of the present invention is to reduce Residual Gas Fraction (RGF) by better scavenging and pumping loss reduction.
[007] Another object of the present invention is to reduce knocking and pre-ignition by decreasing compression end temperature by removing burnt gases from the combustion chamber.
[008] Yet another object of the present invention is to improve engine efficiency by reducing pumping loss.
[009] These and other objects and advantages will become more apparent when reference is made to the following description and accompanying drawings.
SUMMARY OF THE INVENTION:
[0010] This summary is provided to introduce concepts related to exhaust port structure of internal combustion engine. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0011] The present subject matter relates to an exhaust port structure for better scavenging of burnt gases from the combustion chamber of an internal combustion engine. The exhaust port structure includes an exhaust air passageway and a pair of first and second exhaust ports that is branching from the exhaust air passageway toward first and second exhaust valve openings. The exhaust air passageway connects with common exhaust pipe of the vehicle. The first and the second exhaust ports define upper wall and bottom wall divided by port center line. Further, a first valve and a second valve are slidably arranged in the first and the second exhaust valve openings to open and close the first and the second exhaust valve openings to allow passage of burnt gases from the combustion chamber to exhaust pipe. The exhaust port structure has a throat portion that bent from the port center line toward the valve openings. The throat portion curves with a radius sufficiently small to have no effect on directivity of exhaust air flow. The throat portion is provided in between the first and the second exhaust port and the first and the second exhaust valve openings. The throat portion connects the first and the second exhaust port with the first and the second exhaust valve openings.
[0012] In an aspect, the exhaust port structure defines top profile angles (a and ß) and valve angle (?) that plays vital role for enhancement scavenging of burnt gases from the combustion chamber.
[0013] In an aspect, the exhaust port structure has a smooth port radius to avoid flow de-attachment of burnt gases along length of the exhaust port.
[0014] In an aspect, the exhaust port structure has reduced cross section area of port to enhance flow velocity of burnt gases.
[0015] To further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative only but not used to limit scope of the present subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
[0017] Fig. 1 illustrates a general structure of exhaust port structure;
[0018] Fig. 2 illustrates a side profile of exhaust port structure defining valve angle, smooth radius along port length and reduced inner seat diameter, in accordance with the present subject matter;
[0019] Fig. 3 illustrates a top profile angle of the exhaust port structure, in accordance with an embodiment of the present subject matter;
[0020] Fig. 4a illustrates a side view of base exhaust port showing flow de-attachment on floor of port and less flow area from back of the exhaust valve;
[0021] Fig. 4b illustrates side view of optimized exhaust port showing high velocity area on floor and high flow area from back of exhaust port, in accordance with an embodiment of the present subject matter;
[0022] Fig. 5a illustrates top view of base exhaust port showing less and non-uniform coverage of the exhaust valve seat;
[0023] Fig. 5b illustrates top view of optimized exhaust port showing maximum covering of exhaust valve seat with exhaust mass flow, in accordance with an embodiment of the present subject matter;
[0024] Fig. 6 illustrates simulation calculated flow comparison of Base and Optimized structure of exhaust port, in accordance with an embodiment of the present subject matter; and
[0025] Fig. 7 illustrates actual flow measurement comparison of Base and Optimized structure of exhaust ports, in accordance with an embodiment of the present subject matter.
[0026] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DESCRIPTION OF THE PREFERRED EMBODIMENTS:
[0027] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the present disclosure as defined by the appended claims.
[0028] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0029] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a",” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0030] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0031] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0032] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.
[0033] The exhaust port can improve the engine efficiency by reducing the pumping losses. In the pushing out the exhaust gas, work done by the piston is more that reduces the engine efficiency. Further, if exhaust port has sufficient design to escape all burnt gases from the cylinder, it will reduce chances of knocking and pre-ignition in the combustion chamber. Better scavenging of burnt gases decreases compression end temperature in the combustion chamber that improves knocking and pre-ignition performance of the combustion chamber that ultimately effects the engine efficiency.
[0034] Fig. 2 illustrates structure of exhaust port with optimized parameters for better scavenging of burnt gases from the combustion chamber, in accordance with an embodiment of the present subject matter. The exhaust port structure 200 includes an exhaust air passageway and a pair of first and second exhaust ports 201, 202 branching from the exhaust air passageway toward first and second exhaust valve openings 205, 206. Further, both exhaust ports are provided on one side of cylinder line that joins center of each cylinder in the combustion engine. Each of the first and the second exhaust ports 201, 202 defines a port center line 201g along complete length of the exhaust port structure 200. The first and the second exhaust ports 201, 202 has upper wall 201e, 202e and bottom wall 201d, 202d defined along the port center line 201g. The bottom wall 201d, 202d is closer to combustion chamber as compared to the top wall 201e, 202e. The exhaust port structure 200 further includes a first valve 203 and a second valve 204 that are slidably arranged in the first and the second exhaust valve openings 205, 206 to open and close the first and the second exhaust valve openings 205, 206. The first valve 203 and the second valve 204 has stem 203a, 204a, respectively that slides in the stem guide portions 201a, 202a of the first and the second exhaust port 201, 202.
[0035] The exhaust port structure 200 defines a throat portion 201b, 202b that is provided in between the first and the second exhaust port 201, 202 and the first and the second exhaust valve openings 205, 206. The throat portion 201b, 202b is bent portion. The throat portion 201b, 202b can be part of the exhaust port structure 200 or it can be part of combustion chamber. The throat portion 201b, 202b connects the first and the second exhaust port 201, 202 with the first and the second exhaust valve openings 205, 206. The throat portion201b, 202b curves with a radius sufficiently small to have no effect on directivity of exhaust air flow.
[0036] Optimized removal of the combusted charge or burnt gases from the combustion chamber is obtained by well-designed exhaust port that depends upon the key parameters, such as reducing cross section area of port to enhance flow velocity, smooth port radius to avoid flow de-attachment, port top profile angles (a and ß), valve angle (?), and minimizing in valve shrouding/masking. The Flow from the back side of valve shows minimization of valve masking.
[0037] As shown in the fig. 2, the exhaust port structure 200 defines a valve angle (?) in between the cylinder bore centre line 207 and center line 205a, 206a of exhaust valve openings 205, 206. The valve angle (?) is in range of 5°~30° angle along with 15° is the best angle
[0038] Further, Inner Seat Diameter (ISD) of the exhaust valve opening 205, 206 is reduced to increase the exhaust gas velocity for better scavenging. Lower inner seat diameter (ISD) has higher exhaust gas velocity, but must be optimized as per engine power target. The ratio of area of ISD to area of cylinder bore in optimized port is 0.138 whereas in the existing port the ratio is 0.154. Further, lesser the ratio higher the flow velocity supporting better scavenging.
[0039] Again referring fig. 2, the exhaust ports 201, 202 defines smooth and uniform radius as indicated by 201f to avoid flow de-attachment of exhaust gases from the bottom wall 201d, 202d of the exhaust ports 201, 202.
[0040] Referring to fig. 3, the exhaust ports 201, 202 define a port top profile angles (a and ß) in between the port center line 201g and cylinder line 208 or crankshaft axis 208 of engine. For uniform flow of exhaust gases from the combustion chamber, the top profile angle (a) is nearly perpendicular, i.e., 85o to 95o, preferably 90o to the crank axis 208. When the port top profile angles (a) is perpendicular to the crank axis 208, the exhaust gases or combusted charge come directly out of the exhaust valve opening from the combustion chamber without much change in flow direction. Further, the port top profile angle (ß) is in range 80°~100°, preferably in range 88o to 92o, along with 90° is the best angle,
[0041] For testing, a base exhaust port structure is optimized as per the inventive parameters, such as reducing cross section area of port to enhance flow velocity, smooth port radius to avoid flow de-attachment, port top profile angles (a and ß), valve angle (?), and minimizing in valve shrouding/masking.
[0042] Fig. 4a and 4b shows comparison of base exhaust port structure with the present optimized exhaust port structure in respect flow de-attachment on floor of exhaust port and less flow area from back of the exhaust valve. As shown in figure 4a, flow de-attachment as indicated by 501 on the floor or the bottom wall of the exhaust port that creates flow resistance inside the exhaust port ultimately reduce mass flow rate. Further, flow de-attachment 501 is occurred due to sharp radius. As indicated by 502, flow from the back of exhaust valve is less due to high valve shrouding. Referring to fig. 4b, small flow de-attachment as indicated by 501a of exhuast gas or flow is obtained due to less resistance of eddy circulation hence mass flow rate of exhaust gas is improved. Further, higher flow from back of the valve is obtained due to lower shrouding as indicated by 502a. Pressure drop though out system is also reduced to resulting in lower pumping losses of engine.
[0043] Fig. 5a and 5b shows comparison of base exhaust port structure with the present optimized exhaust port structure in respect covering of exhaust valve seat with exhaust mass flow. For better scavenging of exhaust gases from the combustion chamber, the exhaust valve opening must show uniform exhaust mass flow from front as well as back side of the valve seat. As shown in fig. 5a, exhaust port top of base exhaust port structure shows non-uniform flow from exhaust inner valve seat as indicated by 601. The base structure of exhaust port does not utilize the maximum area of exhaust valve seat for flow. Referring fig. 6b, the top view of the exhaust valve where reduced exhaust valve shrouding area support to flow charge uniformly around the exhaust valve as indicated by 601a. This helps to utilize a maximum area of exhaust valve seat for flow most exhaust flow.
[0044] Fig. 6 illustrates simulation calculated flow comparison of Base and Optimized structure of exhaust port. Improvement in simulation for mass flow rate is observed even after reduction of ISD by 1 mm. The ratio of area of ISD to area of cylinder bore in optimized port is 0.138 whereas in the existing port the ratio is 0.154. Further, lesser the ratio higher the flow velocity supporting better scavenging.
[0045] Fig. 7 illustrates actual flow measurement comparison of Base and Optimized structure of exhaust ports. Figure 7 shows improvement in actual testing from base exhaust port structure to the optimized exhaust port structure. In the actual testing of the optimized exhaust port structure, approximately 36% flow improvement has been gained with optimized port with respect to base port structure.
[0046] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”
[0047] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

We claim:
1. An exhaust port structure (200) for improvement in scavenging of burnt gases from combustion chamber, the exhaust port structure (200) comprising:
an outlet air passageway and a pair of first and second exhaust ports (201, 202) branching from the outlet air passageway toward first and second exhaust valve openings (205, 206), the first and the second exhaust ports (201, 202) defines upper wall (201e, 202e) and bottom wall (201d, 202d) along port center line (201g);
a first valve and a second valve (203, 204) are slidably arranged in the first and the second exhaust valve openings (205, 206) to open and close the first and the second exhaust valve openings (205, 206), where stem (203a, 204a) of the first valve and the second valve (203, 204) slides through stem guide portions (201a, 202a); and
a throat portion (201b, 202b) provided in between the first and the second exhaust port (201, 202) and the first and the second exhaust valve openings (205, 206), the throat portion (201b, 202b) connects the first and the second exhaust port (201, 202) with the first and the second exhaust valve openings (205, 206);
characterized in that
wherein uniform radius (201f) provided along the first and the second exhaust port (201, 202) to avoid flow de-attachment of burnt gases from the bottom wall (201d, 202d).
2. The exhaust port structure (200) as claimed in claim 1, wherein a valve angle (?) between central axis (205a, 206a) of the first and second exhaust valve openings (205, 206) and cylinder bore center line (207) is in range of 5°~30°.
3. The exhaust port structure (200) as claimed in claim 1, wherein the first and the second exhaust port (201, 202) define top profile angles (a and ß) that are perpendicular to crank axis (208) (A).
4. The exhaust port structure (200) as claimed in claim 3, wherein the top profile angle (a) is in range 85°~95°, preferably 90o.
5. The exhaust port structure (200) as claimed in claim 3, wherein the top profile angle (ß) is in range 80°~100°, preferably in range 88o to 92o.
6. The exhaust port structure (200) as claimed in claim 1, wherein the first and the second exhaust ports (201, 202) are positioned on one side of the cylinder line.
7. The exhaust port structure (200) as claimed in claim 1, wherein ratio of area of Inner Seat Diameter (ISD) of the exhaust valve opening (205, 206) to area of cylinder bore is approximately 0.138.