Gas separation: processes – Deflecting – Centrifugal force
Reexamination Certificate
2001-12-11
2003-04-22
Hopkins, Robert A. (Department: 1724)
Gas separation: processes
Deflecting
Centrifugal force
C055S394000, C055SDIG003, C096S384000, C062S005000
Reexamination Certificate
active
06551385
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to methods and devices for managing the liquid and gaseous components of a variable pressure stream. More particularly, embodiments of the present invention relate to an exhaust emissions separator for management of internal combustion engine exhaust components.
2. State of the Art
The popularity and widespread use of two-stroke engines is undisputed. Such engines are in extensive use throughout the United States, as well as in both industrialized and developing nations around the world. In particular, two-stroke engines are the power source of choice in such varied applications as snowmobiles, outboard motors, all-terrain vehicles, off-road vehicles, scooters, mopeds, lawn mowers, and chain saws, to name but a few. The typical two-stroke engine possesses a variety of features which make it ideally suited for such applications.
One such feature is the relative simplicity of the two-stroke engine. In general, the two-stroke engine possesses relatively few moving parts and components as compared to, for example, the more complex four stroke engine, so that operation and maintenance of the two-stroke engine is relatively simple. Further, because of this simplicity, a two-stroke engine is less likely to experience the breakdowns and failures that characterize more complex engines, and is thus somewhat more reliable. Another consequence of the relative simplicity of the two-stroke engine is that because the two-stroke engine utilizes relatively few parts, it can be readily produced at relatively low cost.
The simplicity of the two-stroke engine has other important consequences as well. For example, because of the relatively few parts employed in typical two-stroke engine designs, the two-stroke engine can be made very compact and light in weight. As a direct result of its light weight, the typical two-stroke engine has a relatively high power to weight ratio (PWR). The relatively high PWR of the typical two-stroke engine makes it ideally suited for applications, such as those noted above, where a relatively large amount of power is required, but where excessive engine weight would likely compromise the overall performance of the device.
While two-stroke engines possess numerous advantages, such engines are not without their shortcomings. A major shortcoming of typical two-stroke engines is their propensity to discharge exhaust containing a relatively large amount of unburned fuel and/or oil. This characteristic is primarily a consequence of the construction of the engine. In general, two-stroke engines operate in such a way that the vacuum created in the combustion chamber by the exit of pressurized exhaust serves to pull a fresh volume of unburned fuel and oil into the combustion chamber, preparatory to the compression stroke. As a result of the substantially simultaneous exit of exhaust and entry of unburned fuel, some of the unburned fuel and/or oil are pulled from the combustion chamber along with the exhaust, and discharged, unburned, to the atmosphere.
The omission of unburned oil and gas from the two-stroke engine exhaust is problematic for a number of reasons. First, any unburned gas omitted is necessarily gas that is not available for operation of the engine. Thus, the operational efficiency of the engine with regard to a given amount of fuel is significantly compromised. In fact, it is estimated that as much a twenty five percent to thirty five percent of the fuel that enters a typical two-stroke engine exits unburned with the exhaust. Thus, while they possess other significant advantages, two-stroke engines are not particularly fuel-efficient.
While the emission of unburned fuel, oil, and other heavy hydrocarbons, is of some interest insofar as the fuel efficiency of two-stroke engines is concerned, another significant effect of such emissions is the severe impact that they have on the environment. For example, the discharge of raw engine oil and fuel from outboard engines is a major cause of pollution in both fresh-water and salt-water waterways. It is estimated that nearly 166,000,000 gallons of petroleum products are discharged into the waterways of the United States alone each year. This high volume of pollutants is a direct consequence of the ubiquity of two-stroke engines and their operational characteristics.
Pollution generated by outboard engines, jet skis, and other water-based platforms is not limited solely to waterways however. At least some of the unburned fuel, oil, and heavy hydrocarbons are emitted as vapor from the engine. Thus, the two-stroke engines typically employed in water-based platforms pollute the air as well as the water. Pollution of the air is further exacerbated by land-based two-stroke engine platforms such as snowmobiles, chain saws, weed trimmers, motorcycles, and the like. Air pollution resulting from two-stroke engines is particularly problematic in developing nations where the two-stroke engine is widely used in personal transportation applications. Finally, these land-based platforms also pollute the soil, and consequently the groundwater, when they discharge oil and fuel onto the ground. The negative impacts of such pollution on the environment as well as humans and animals are well-documented. Consequences associated with such pollution include, but are not limited to, respiratory distress, aquatic toxicity and mutagenicity.
The multitude of problems induced by the operation of two-stroke engines has not gone unnoticed. The manufacturers and users of such engines have come under substantial pressure, from regulatory agencies, environmental groups, and the like to severely restrict, if not cease all together, the manufacture and/or use of two-stroke engines. For example, the use of such engines has been banned in at least some national parks. Further, it appears that actions such as use bans and the like are likely to become increasingly commonplace as the protest against the use of two-stroke engines gains momentum.
In response to such pressures, and in an effort to preserve the viability of two-stroke engine based applications, industry has made a number of attempts to resolve the pollution problems inherent in two-stroke engines. As discussed below however, unacceptable costs and/or drawbacks are associated with virtually all of these attempts.
One such attempt at managing two-stroke engine exhaust emissions has focused on improving the performance characteristics of small four-stroke engines in an attempt to adapt these four-stroke engines for at least some of the typical two-stroke engine applications. In particular, attempts have been made to implement a multiple valve arrangement in small four-stroke engines, such as has been done with four-stroke engines used in transportation applications. While arguably improving performance to some degree, such arrangements have increased the complexity of the modified four-stroke engines and have done little or nothing to reduce their weight. Thus, the relatively high PWR that is characteristic of two-stroke engines has not been preserved in these modified four stroke engines. As discussed earlier, a high PWR is critical for high performance lightweight vehicles such as snowmobiles, motor strokes, mopeds, lawn trimmers, lawn mowers, and the like.
Still other attempts to reduce and/or control emissions from two-stroke engines have been directed towards modifications of the process and devices used to introduce fuel into the cylinder. One such approach is commonly known as direct fuel injection (DFI). In contrast with more conventional two-stroke engines, a DFI two-stroke engine directly and independently directs fuel into the cylinder, rather than using the crankcase as a scavenging pump to draw oil and fuel from the carburetor to the cylinder. When properly designed and implemented, DFI systems have proven to be somewhat successful in reducing the emissions of two-stroke engines.
Any success achieved with DFI engines has come with significant attendant costs however. For example, the fuel injec
McKellar Michael G.
Raterman Kevin T.
Turner Terry D.
Wilding Bruce M.
Bechtel BWXT Idaho LLC
Hopkins Robert A.
Trask Britt PC
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