GASEOUS FUELED TWO-STROKE ENGINE
An engine according to various embodiments generates reduced emissions.
The present application claims the benefit of priority of U.S. provisional patent application No. 61/306,569, entitled “GASEOUS FUELED TWO-STROKE ENGINE”, and filed Feb. 22, 2010, the entirety of which is incorporated by reference herein for all purposes.
BACKGROUNDConventional two-stroke engines used in India and worldwide have certain disadvantages as they have high levels of pollutants in the exhaust pipe. This is primarily caused by lack of intake and exhaust valve as in the four-stroke engines, and secondly due to scavenging loss of fresh charge through the exhaust, and thirdly the fixed percent of oil is pre-mixed with fuel that does not readily burn during part throttle, and fourth due to liquid fuel as in gasoline engines does not vaporize readily. Most importantly, the exhaust gas has fractions of many different hydrocarbon species that is harder to treat by low cost catalysts.
It is known in the engine industry that there are gaseous fueled two-stroke engines with oil injection system. However, these engines do not have variable oil injection system and secondly do not have exhaust gas treatment to clean up the pollutants in the tail pipe.
The design described here according to some embodiments has a gaseous fueled two-stroke engine with oil injection system and a special catalyst to treat the hydrocarbon originating from the gas fuel, more particularly Propane fuel (commonly known as LPG) and Butane fuel as well as unburned hydrocarbon from the lubricating oil and a system to regulate percent of oil injected according to the operating ranges of the engine. The engine can be used in many hand-held applications such as trimmers, blowers, mopeds, and scooters.
SUMMARYAccordingly, designs according to various embodiments provide new and improved methods of operating and having a cleaner gaseous fueled small two-stroke engine for many applications.
The low cost simpler two-stroke engine may be especially suited for hand-held, lawn and garden equipments such as trimmers, blowers, chainsaws, generator engines, and mopeds.
Various embodiments reduce the pollutants significantly while operating on gaseous fuel, more so with Propane (commonly known as LPG), Butane and natural gas.
Further, various embodiments provide a new and improved lubricating system where in the oil injection pump is driven off of the crankshaft for a positive oil feed into the engine and also regulated for optimum percent/amount of oil injected into the engine according to operating conditions of the engine. The oil pump can also be a diaphragm type operated due to pulsation in the crankcase chamber. Secondly, the oil is regulated by means of a link to the throttle valve, or intake manifold pressure or speed governor attached to the control system in the pump. The link can be from the throttle valve regulating the air-fuel in the carburetor or a pressure sensitive diaphragm in the intake.
The exhaust muffler 128 is connected to the exhaust port and the exhaust muffler has an exhaust outlet 132 and a catalyst element 130 inside the exhaust muffler 128. There are many ways how the catalyst is mounted inside the exhaust muffler. Closer to the exhaust port is preferred; however, it may be mounted on a plate between the two shelves (not shown) of the exhaust muffler. In conventional petrol two stroke engines, the petrol is mixed with the lubricating oil in a certain ratio, ranging from 25:1 to 50:1. However, in a gaseous fueled two-stroke engine, the oil is inducted into the crankcase chamber through the intake manifold 126 or is directly injected into the crankcase chamber 108 using either gravity feed combined with the sub atmospheric pressure during intake or using a separate oil injection pump 138 driven by the crankshaft 106, as shown in
Another aspect of the engine with catalytic muffler is that a secondary air may be inducted through check valve into the manifold to improve converter efficiency. Yet, another aspect of the engine may be a temperature sensor on the engine block to shut off the engine in case engine runs hotter than pre-determined temperature due to lack of lubricating oil. The sensor is connected to the ignition coil for supply of power to operate the electronic sensor. Alternatively a pressure sensor in the oil delivery system may be incorporated or even an oil level sensor may be used as safety measure to protect the engine. Another aspect of the temperature sensor is that the control logic determines if the temperature difference between ambient temperature and engine block temperature is greater than the pre-determined range to shut off the engine. The power supply for the electronic control system may be from separate power coil 328 or built into the primary ignition coil 324 in the ignition coil. The ignition could be cut off based on the oil pressure sensor in the oil outlet line 146 (sensor not shown). It is also possible to have an oil level sensor to cut off ignition when the oil level is below the predetermined level. Also, it is possible to have a bimetal temperature sensor to cut off ignition when the temperature exceeds a predetermined engine temperature. The bimetal temperature sensor may be linked to the carburetor to cut off fuel when the temperature exceeds predetermined level.
During the scavenging process, both the exhaust and transfer ports are open and this causes a fraction of the charge coming into the combustion chamber to escape through the exhaust port 134, which is the root cause for higher pollutants in the two-stroke engine. It is estimated that up to 30 percent of the charge escapes during the scavenging process and is commonly called short circuiting of charge. Some advanced engines use air-head concept (stratified engines) as published in U.S. Pat. No. 6,901,892 and U.S. Pat. No. 4,075,985 to minimize the short circuit loss of fuel. The exhaust gas mixed with unburned fuel (un-burnt hydrocarbons) escapes into the atmosphere after passing through the exhaust muffler 128 and the exhaust outlet 132. If the exhaust gas is not treated, the exhaust gas will have a variety of potentially toxic carbonaceous air pollutants. Pollutant is also known to cause cancers and respiratory diseases. Conventional two-stroke engines use catalysts in the exhaust muffler to clean the exhaust gas and reduce the levels of pollutants in the tail pipe exhaust gas. However, in a petrol engine, the oil is mixed at a fixed ratio, and importantly a variety hydrocarbon species is found in the exhaust gas. Thus composition of the catalyst has to be able to burn most of the species. Secondly, the particulate matters (PM) in petrol fueled two-stroke engine is significantly higher and the catalyst helps burn off some PM. However, in an LPG or Butane fueled two-stroke engine, since the fuel is already in gas form, the PM is almost zero and species of unburned hydrocarbon in the exhaust gas is very narrow and mostly propane or butane. As such treatment of the exhaust gas is easier with specific catalytic material. Particularly if the air-fuel mixture is lean, then it requires mostly reduction catalyst such as palladium. The use of catalytic muffler 128 in conjunction with the air-head engine will further reduce the exhaust pollutants.
- 100 Gaseous fueled hand held engine with catalytic muffler
- 200 Gaseous fueled rotary valve engine with catalytic muffler and oil pump
- 101 LPG Engine block
- 102 Cylinder
- 104 Crankcase
- 105 Crankcase chamber
- 106 Crankshaft
- 107 Transfer passage
- 108 Combustion chamber
- 109 Transfer passage
- 110 Piston
- 112 Connecting rod
- 114 Piston pin
- 116 Crank pin
- 117 Cut out A
- 118 Crank (crank web)
- 119 Cut out B
- 120 Spark plug
- 122 Carburetor assembly
- 123 Throttle valve
- 124 Gaseous fuel carburetor
- 125 Air filter
- 126 Intake manifold
- 128 Exhaust muffler
- 130 Catalyst element
- 132 Exhaust outlet
- 134 Exhaust port
- 136 Intake port
- 137 Transfer port
- 138 Oil pump
- 140 Oil tank
- 142 Oil inlet to pump
- 143 Oil supply line in the tank
- 146 Oil outlet to the intake
- 148 Oil feed with heavy filter
- 150 Gaseous fuel tank
- 152 High pressure fuel line
- 154 Gas pressure regulator
- 156 Low pressure fuel line
- 162 Throttle valve
- 164 Throttle shaft
- 166 Linkage
- 168 Oil control system
- 200 Boom
- 300 String trimmer
- 304 Housing
- 320 Engine temperature sensor
- 324 Ignition coil
- 326 Ambient temperature sensor
- 328 power coil
- 404 low pressure regulator
- 406 Metering chamber
- 408 Carburetor body
Various embodiments have been described in an illustrative manner. It is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. While there have been described herein, certain exemplary embodiments, other modifications shall be apparent to those skilled in the art from the teachings herein and, it is, therefore, desired to be secured in the appended claims all such modifications as fall within the true spirit and scope of the described and contemplated embodiments.
Claims
1. A gaseous fueled two-stroke engine 100 having a carburetor for gaseous fuel 124 with an oil injection pump 138 driven by a crankshaft 106 with an LPG or Butane fuel tank attached to the engine and a separate oil tank 140 and having a catalytic muffler 128 to reduce engine out unburned emissions from a gaseous fuel, and unburned emissions generated from oil, where the exhaust total emissions from muffler outlet are less than 50 gm/kw-hr.
2. The engine as claimed in 1, having an intake port 136 and a temperature sensor to sense an ambient temperature at the intake port and to cut off ignition when the difference between the ambient temperature and an engine temperature is above a predetermined level.
3. The engine as claimed in 1, having an oil pressure sensor to cut off ignition when an oil pressure in the oil outlet pressure is below a predetermined level.
4. The engine as claimed in 1, having an oil level sensor in the oil tank 140 to cut off ignition when an oil level in the oil tank 140 is below a predetermined level.
5. The engine as claimed in claim 1 having a catalytic muffler 128 for reducing exhaust emissions, in which the engine is a gaseous fueled small engine less than 100 cc.
6. The engine according to claim 2 in which the muffler 128 includes a catalyst element 130 to reduce unburned propane fuel and unburned hydrocarbons generated from oil.
7. The engine according to claim 2 in which the muffler 128 includes a catalyst element 130 to treat the unburned butane fuel.
8. The engine according to claim 2 in which the muffler 128 includes a catalyst element 130 to treat unburned hydrocarbon.
9. The engine according to claim 2 in which the muffler 128 includes a catalyst element 130 to reduce NOx, in which the engine is a lean burn gaseous fueled two-stroke engine.
10. The engine according to claim 2 in which the muffler 128 includes a catalyst element 130 to oxidize unburned hydrocarbon in exhaust gas.
11. The engine as claimed in claim 2 having Propane (LPG) as a fuel.
12. The engine as claimed in claim 2 having Butane as a fuel.
13. The engine as claimed in claim 1, in which the oil injection pump is a variable rate oil injection pump injecting substantially less oil per hour at idle speed than the oil injection rate at maximum speed.
14. The engine as claimed in claim 1, in which the oil injection pump is a speed governed oil injection pump.
15. The engine as claimed in claim 1, in which the oil injection pump is a throttle piston governed oil injection pump.
16. The engine as claimed in claim 1, further including an electronic temperature sensor.
17. The engine as claimed in claim 1, further including a bimetal temperature sensor to cut off the engine in the event that oil fails to be delivered to the engine, in order to protect against engine failure in such circumstances.
18. The engine as claimed in claim 1 having an oil feed system having all attitude oil inlet 148 and shape of an all attitude oil tank 140.
19. The engine as claimed in 1, in which the engine is a stratified two-stroke engine.
20. The engine of claim 14 in which the oil feed system includes an oil feed line 148 that is rotatably mounted in the oil tank and has flexible oil line.
21. A gaseous fueled two-stroke engine 100 having a gaseous carburetor 124 with an oil injection pump 138 driven by a crankshaft 106 with an LPG or Butane fuel tank attached to the engine and a separate oil tank 140 shaped such as to access oil at all engine attitudes and having a catalytic muffler 128 to treat the exhaust gas where the exhaust emissions are no more than 50 gm/kw-hr and the oil consumption is between 1.2 to 6% of fuel consumption rate.
22. A gaseous fueled two-stroke engine 100 having a carburetor for gaseous fuel 124 with an variable rate oil injection pump 138 driven by a crankshaft 106 with an LPG or Butane fuel tank attached to the engine and a separate oil tank 140 and having a catalytic muffler 128 to reduce high engine out emissions to exhaust gas where the exhaust emissions are less than 50 gm/kw-hr and the gaseous fuel is substantially free of pre-mixed oil.
23. A gaseous fueled two-stroke engine 100 having a carburetor for gaseous fuel 124 with an oil injection pump with a gaseous fueled tank attached to the engine and a separate oil tank 140 shaped such as to access oil at all engine attitudes and having a catalytic muffler 128 to treat the exhaust gas where the exhaust emissions are less than 50 gm/kw-hr and the gaseous fuel is substantially free of pre-mixed oil.
Type: Application
Filed: Jan 23, 2011
Publication Date: Aug 25, 2011
Inventors: Jay Sirangala Veerathappa (Northridge, CA), Sharu Rajgiri (Suwanee, GA)
Application Number: 13/011,925