Patent Publication Number: US-11643962-B2

Title: System and method for low CO emission engine

Description:
RELATED APPLICATIONS 
     The present application is a continuation of U.S. application Ser. No. 16/318,123, filed Jan. 15, 2019 which claims the priority benefit of International Patent Application No. PCT/2017/47561, filed Aug. 18, 2017 which claims the priority benefit of Provisional Patent Application No. 62/376,997, filed Aug. 19, 2016, which is incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure generally relates to engines and, more particularly, to low emission engines. 
     BACKGROUND 
     Low emission engines can help reduce greenhouse gas emissions levels, air-borne pollutants and other impacts to the environment. 
     SUMMARY 
     According to one aspect, systems and methods provide a small gasoline engine with a catalyst positioned downstream of an exhaust valve. 
     Other systems, methods, features, and advantages is or will become apparent upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description and be protected by the accompanying claims. 
     According to one aspect, a system is provided and includes an engine including an exhaust valve, an exhaust manifold downstream of the exhaust valve and a muffler downstream of the exhaust manifold. The system also includes a catalyst positioned downstream of the exhaust valve. 
     According to one aspect, the engine may be a four-stroke gasoline engine. 
     According to one aspect, the system may further include a portable generator configured to be powered by the engine. 
     According to one aspect, the portable generator may include a frame at least partially supporting the engine and at least one wheel coupled to the frame. 
     According to one aspect, the portable generator may provide power less than or equal to about 10 kilowatts. 
     According to one aspect, the engine may be between about 80 cubic-centimeters and about 224 cubic centimeters. 
     According to one aspect, the engine may be between about 224 cubic-centimeters and about 999 cubic centimeters. 
     According to one aspect, the engine may be less than about 80 cubic-centimeters. 
     According to one aspect, the catalyst may be positioned in the muffler. 
     According to one aspect, a cross-section of the muffler may be oval shaped. 
     According to one aspect, the muffler may include an entrance cone for the catalyst. 
     According to one aspect, the catalyst may be positioned in the exhaust manifold. 
     According to one aspect, the system may further include an oxygen sensor positioned upstream of the catalyst. 
     According to one aspect, the catalyst and the oxygen sensor may be positioned in the exhaust manifold. 
     According to one aspect, the oxygen sensor may be positioned about 1 inch from the exhaust valve. 
     According to one aspect, the catalyst may be positioned between about 4 inches to about 10 inches from the exhaust valve. 
     According to one aspect, the catalyst may be positioned about 6 inches from the exhaust valve. 
     According to one aspect, the catalyst may be one of a plurality of catalysts. 
     According to one aspect, the engine may include a plurality of cylinders and the exhaust manifold may include a first portion associated with one of the plurality of cylinders and a second portion associated with another one of the plurality of cylinders. The catalyst may be a first catalyst positioned in the first portion of the exhaust manifold. The system may further include a second catalyst positioned in the second portion of the exhaust manifold. 
     According to one aspect, the system may further include a plurality of oxygen sensors. One of the plurality of oxygen sensors may be positioned in the first portion of the exhaust manifold and another one of the plurality of oxygen sensors may be positioned in the second portion of the exhaust manifold. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In association with the following detailed description, reference is made to the accompanying drawings, where like numerals in different figures can refer to the same element. The features of the drawings are not necessarily drawn to scale. 
         FIG.  1    is a schematic of an example engine emission reduction system. 
         FIG.  2    is a schematic of a side-cutaway view of a portion of the example engine emission reduction system. 
         FIG.  3    is a schematic of an example muffler capable of being included in the engine emission reduction system. 
         FIG.  4    is a schematic of an example muffler capable of being included in the engine emission reduction system. 
         FIG.  5    is a top perspective view of an example device in which the engine emission reduction system may be incorporated. 
         FIG.  6    is an elevational view of one example of a portion of an engine emission reduction system with examples of catalysts and examples of oxygen sensors positioned in an exhaust manifold. 
         FIG.  7    is an elevational view of one example of a portion of an engine emission reduction system with examples of catalysts and examples of oxygen sensors positioned in an exhaust manifold 
     
    
    
     DETAILED DESCRIPTION 
     While the disclosure may be susceptible to embodiment in different forms, there is shown in the drawings, and herein is described in detail, a specific embodiment with the understanding that the present disclosure is to be considered an exemplification of the principles of the disclosure, and is not intended to limit the disclosure to that as illustrated and described herein. Therefore, unless otherwise noted, features disclosed herein may be combined together to form additional combinations that were not otherwise shown for purposes of brevity. It is further appreciated that in some embodiments, one or more elements illustrated by way of example in a drawing(s) may be eliminated and/or substituted with alternative elements within the scope of the disclosure. 
     Referring to  FIG.  1   , an engine emission reduction system (hereinafter referred to more simply as a “emission reduction system”)  2  in accordance with at least one embodiment includes an engine  4 , a muffler  6 , electronic fuel injection (EFI) system  8  and/or exhaust manifold  10 . In some embodiments, the muffler  6  includes a catalyst  12 , but the catalyst  12  can be included in various other positions within the emission reduction system  2 , as described in more detail below. The catalyst  12  can also be referred to as a catalytic converter. The engine emission reduction system  2  may be utilized with a large variety of engines  4  and all of such possibilities are intended to be within the spirit and scope of the present disclosure. In some embodiments, the engine  4  can include a small utility internal combustion engine, e.g., about 225 to about 999 cc, capable of being employed in a variety of applications including, for example, a variety of types of power machinery. For example, the engine  4  can include a four-stroke, twin cylinder KOHLER™ CH440 internal combustion engine manufactured by Kohler Company of Kohler, Wis. In some embodiments, the engine  4  may include any number of cylinders including one, twin or more cylinders. Also, in some embodiments, the engine  4  may be air cooled or liquid cooled. Further, in some embodiments, the engine  4  may have a vertical orientation or a horizontal orientation. Although not shown, it will be understood that in some cases the engine  4  can be employed to provide power in chipper/shredders, power washers, edgers, pumps, tillers, pressure washers, aerators, portable generators (e.g., from one to ten KW and/or able to be hand carried or moved by a person), log splitters, dethatchers, tamper/plate compactors, and other small equipment, etc. In some embodiments, it is also possible the emission reduction system  2  of  FIG.  1    or other embodiments of emission reduction systems are implemented in conjunction with other types of engines (e.g., other than small utility engines) and/or in conjunction with other types of applications and/or equipment. 
     In  FIG.  1   , it is envisioned that the emission reduction system  2  provides a very low carbon-monoxide-emitting, portable gasoline engine, e.g. having one or two cylinders. In some embodiments, other numbers of cylinder engines can use the emission reduction system  2 . The emission reduction system  2  can be installed by the engine&#39;s manufacturer, however, it is also envisioned that the emission reduction system  2  can be sold as an after-market add-on product capable of being installed by a party other than the engine&#39;s manufacturer. Additionally, in at least some of the embodiments, the emission reduction system  2  is implemented in conjunction with the engine  4 , the muffler  6  and/or the EFI  8 . Nevertheless, the emission reduction system  2  can be used with other types of engine components as well, and need not necessarily be utilized with the engine  4 , the muffler  6  and/or the EFI  8 . 
     One example of a device in which the emission reduction system  2  may be used is illustrated in  FIG.  5   . In this illustrated example, the device is a portable generator  30  and includes a frame  32 , at least one wheel  34  coupled to the frame  30  (two wheels  32  in the illustrated example), and at least one handle  36  coupled to the frame  30  (two handles  36  in the illustrated example). In some embodiments, the portable generator  30  may include air cooled. In some embodiments, the portable generator  30  may provide about 10 kilowatts or less of power. In some embodiments, the portable generator  30  may be a Class 1 generator, a Class 2 generator or less than a Class 1 generator. A Class 1 generator may be defined as having an engine size of between about 80 cc (cubic-centimeter) to about 224 cc. A Class 2 generator may be defined as having an engine size of between about 224 cc to about 824 cc or 999 cc. In some embodiments, the portable generator  30  may have an engine size less than 80 cc. It should be understood that the portable generator  30  is only one example of the many types of devices in which the emission reduction system  2  may be utilized. Accordingly, the inclusion of the portable generator is not intended to be limiting upon the present disclosure, but is rather provided to demonstrate at least some of the principles of the present disclosure. 
       FIG.  2    is a schematic of a side-cutaway view of the example engine emission reduction system  2 . In some embodiments, the catalyst  12  is positioned downstream from an exhaust valve  14 . Downstream is determined by a flow direction of exhaust in the engine emission reduction system  2 . The flow direction is represented by arrow F in  FIG.  2   . The exhaust valve  14  controls a release of exhaust from the engine  4 , through the exhaust manifold  10  connected on one end with an exhaust port  16  and on the other end the muffler  6 . In some embodiments, for example in  FIGS.  3  and  4   , the catalyst  12  is embedded or included in the muffler  6 , e.g., a stainless-steel muffler, a low carbon steel, etc. Positioning the catalyst  12  in the muffler  6  may increase a life of the catalyst  12 . In embodiments with the catalyst  12  positioned in the muffler  6 , the muffler  6  may be made of stainless steel. In some embodiments, for example in  FIGS.  6    and  7 , the catalyst  12  is positioned in the exhaust manifold  10 . For example, the catalyst  12  can be positioned in a can in piping of the manifold  10 . Positioning the catalyst  12  in the manifold  10  may result in better performance of the catalyst  12 . For example, reactions may still be taking place or a higher quantify of reactions are taking place in the manifold  10  versus further downstream. The catalyst  12  may perform better at reducing emissions in this environment than at positions further downstream. In embodiments with the catalyst  12  positioned in the manifold or locations other than the muffler  6 , the muffler  6  may be made of low carbon steel or a different material other than stainless steel. In some embodiments, the catalyst  12  is positioned close to the exhaust valve  14 , e.g., within about eight to about twenty-four inches of the exhaust valve  14 . In some embodiments, the catalyst  12  is positioned close to the exhaust port  16 , e.g., within about eight to about twenty-four inches of the exhaust port  16 . In some embodiments, the catalyst  12  is positioned within the exhaust port  16 . In a multi-cylinder engine  4 , in some embodiments, there may be a catalyst  12  for each cylinder. Positioning the catalyst  12  in these manners relative to exhaust valve  14 , exhaust port  16 , etc. may be referred to as close coupled. That is, the catalyst  12  is close coupled to the exhaust valve  14 , exhaust port  16 , etc. Close coupling the catalyst  12  relative to these components of the engine emission reduction system  2  can provide temperature and/or performance advantages. In some embodiments, catalyst  12  may be positioned about 6 inches from the exhaust valve  14 . In some embodiments, the catalyst  12  may be positioned between about 4 to 10 inches from the exhaust valve  14 . In some embodiments, the catalyst  12  may be positioned between about 1 to about 24 inches. In some embodiments, the catalyst  12  is ceramic. In some embodiments, the catalyst  12  is metallic. 
     With continued reference to  FIG.  2   , in some embodiments, one or more oxygen (O2) sensor(s)  18  are positioned in the exhaust manifold  10 . The O2 sensor(s)  18  can be positioned a determined distance, e.g., about 0.25 to about ten inches, from the exhaust valve  14 . In some embodiments, the O2 sensor may be positioned about six inches from the exhaust valve  14 . In some embodiments, the O2 sensor may be positioned about 1 inch form the exhaust valve  14 . In some embodiments, the O2 sensor(s)  18  can be positioned a determined distance from the exhaust port  16 . In some embodiments, the O2 sensor(s)  18  can be positioned before or upstream of the catalyst  12  with regard to a direction of the exhaust. In some embodiments, the O2 sensor(s)  18  may be positioned between the catalyst  12  and the exhaust valve  14 . In some embodiments, the O2 sensor(s)  18  can be positioned before or upstream of the exhaust manifold  10 , e.g., in the cylinder head  20 . 
     In some embodiments, the engine  4  may include multiple cylinders. In such embodiments, the engine emission reduction system  2  may include a separate catalyst  12  and separate O2 sensor  18  for each cylinder of the engine  4 . For example, with reference to  FIGS.  6  and  7   , the engine emission reduction system  2  includes a catalyst  12  and an O2 sensor  18  for each cylinder (two cylinders in the illustrated examples). 
     A transport distance of the fuel injector  8  to the O2 sensor  18  can affect an A:F dithering speed of the fuel into the exhaust stream. In some embodiments, minimizing or reducing the transport distance may speed-up the feedback of the system. 
     In some embodiments, the catalyst  12  may include a rare earth metal that absorbs O2 and wash coat to reduce pollutants including hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxide (NOx). Many types of catalyst  12  can best reduce HC and CO when the engine  4  is run lean of stoichiometric (e.g., 14.7:1), e.g., about 15:1 lean. However, in some of these systems, NOx may be best reduced when the engine  4  runs rich, e.g., about 13.9:1 rich. With intentional dithering, the fuel injector  8  can be calibrated to run the engine  4  rich/lean/rich/lean for a determined amount of time, e.g., on the order of seconds. In some embodiments, a dithering frequency may be about 0.5 to about 4 Hz. The dithering can allow the catalyst  12  to re-oxygenate and best control the three main chemical pollutants, CO, NOx and HC, present in the exhaust. Additionally or alternatively, the dithering can be used to find a stoichiometric point of the engine  4 . 
     A controller connected integrated with the fuel injector  8 , and/or operably connected with the fuel injector  8 , can control the rich/lean, etc. dithering speed and amplitude. The controller can include one or more processors and one or more memory devices. The memory can include one or more of a program memory, a cache, random access memory (RAM), a read only memory (ROM), a flash memory, a hard drive, etc., and/or other types of memory. In some embodiments, the memory can store instructions (e.g., compiled executable program instructions, uncompiled program code, some combination thereof, or the like)), which when performed (e.g., executed, translated, interpreted, and/or the like) by the processor, causes the processor to perform the dithering and any other processes described herein. 
       FIGS.  3 - 4    are schematics of example implementations of the muffler  6 . The muffler  6  can include double walls  20 , e.g., to improve heat related performance of the catalyst  12  and noise performance of the muffler  6 . A chamber  22  in front of the catalyst  12  can be sized for better exhaust flow distribution to the catalyst  12 . In some embodiments, a catalyst volume is about 0.25 to about 0.75 of a volume of the chamber  22 . In some embodiments, the surface area and air flow through the catalyst  12  can be optimized with a determined geometry of the interior of the muffler  6 , e.g., by making one of the muffler partitions into a catalyst entrance cone  24 , e.g., to funnel air to the catalyst  12 . The shape of the entrance cone  24  can assist with maximizing an amount of surface area of the catalyst  12  impacted by the exhaust. In some embodiments, a cross section of the muffler  6  with a catalyst  12  is shaped like an oval (race-track). In other embodiments, other shapes can be used such as, for example, circular, polygonal perimetered shapes, arcuately perimetered shapes, or a combination of polygonal and arcuately perimetered shapes. 
     While particular embodiments are illustrated in and described with respect to the drawings, it is envisioned that those skilled in the art may devise various modifications without departing from the spirit and scope of the appended claims. It will therefore be appreciated that the scope of the disclosure and the appended claims is not limited to the specific embodiments illustrated in and discussed with respect to the drawings and that modifications and other embodiments are intended to be included within the scope of the disclosure and appended drawings. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and/or functions, it is appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the disclosure and the appended claims. 
     Many modifications and other embodiments set forth herein will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.