| Revision as of 04:17, 19 November 2006 editSno2 (talk | contribs)288 editsm Changed supposed nitrous oxide emmision problem paragraph← Previous edit | Revision as of 06:36, 19 November 2006 edit undoSno2 (talk | contribs)288 edits Added simplified explanation of Bourke engine operationNext edit → | ||
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| ** Eliminate the need to mix oil with the fuel as with standard 2-cycle engines | ** Eliminate the need to mix oil with the fuel as with standard 2-cycle engines | ||
| ** Prevents the ] blow by from polluting the crankcase oil extending the life of the oil | ** Prevents the ] blow by from polluting the crankcase oil extending the life of the oil | ||
| == Simplified explanation: == | |||
| The Bourke engine should be considered an "explosion" engine because of the extremely fast burn time of the fuel air mixture. | |||
| The rising piston compresses the mixture heating it, because of the cool piston head and cylinder walls the mixture is not heated enough to start a burn. The piston "latches" at top dead center do to the action of the scotch yoke. Spark plug fires causing an explosive burn. All of fuel is burned completely because of explosive burn time. Sharp rise in pressure causes scotch yoke to "unlatch" piston. Piston moves down cylinder, expanding gasses following piston cause cooling of piston and cylinder walls. Since all of fuel was burned during "latching" of piston no fuel is being burned at this time, no heat is being added, all expansion results in cooling. When piston reaches the bottom of the cylynder it again "latches" until "unlatched" by the explosion in the opposite cylynder. This gives time for scavaging of explosive gases. | |||
| The mixture must be lean enough so that compression heating of the mixture does not cause it to ignite prior to the "latching". If this occurs engine will not run, or will run rough. Mixture of the fuel must be in the "explosive" range for the engine to run correctly. | |||
| The maximum pressure on the piston occurs right after the release of the piston from top dead center. It is not spread over the whole length of the piston travel as in a conventional engine. For this reason this is an extremely high torque engine. | |||
| The complete burn of the fuel while the piston is "latched" gives this engine its high efficiency and low emmissions. | |||
| The cooling caused by the expanding gases, behind the piston head and the non burning of fuel while piston is traveling, causes the low temperature exaust gases. This also prevents dieseling during the next compression cycle, because of the cooling of the piston head. | |||
| == External links == | == External links == | ||
Revision as of 06:36, 19 November 2006
The Bourke engine was designed by Russell Bourke in the late 1930s, who endeavored to improve upon the Otto cycle engine. Despite finishing his redesign and building several working engines; bad luck (World War II breaking out), bad health and a know-best attitude compounded to prevent his engine from ever coming to market despite its claimed advantages. Well into the 2000's there are several small groups extolling the virtues of the design. The Bourke engine has two opposed cylinders with the pistons in a Scotch yoke mechanism. Because the motion of the pistons is a perfect sine wave with regards to time vs displacement the fuel burns in a smaller volume, and so burns hotter. The Bourke engine also has a looser coupling with the output shaft, preventing excess vibration. The intake valves are replaced by ports, saving on parts.
It is thought that the design features that increase its efficiency create emission problems. The higher combustion temperatures combined with the increased cycle time around top-dead-center lead to increased nitrogen oxide emissions. There have not been any verified nitrous oxide tests on running engines to verify this emmision problem.
Design features
- Scotch yoke instead of connecting rods to translate motion to rotary motion
- Fewer moving parts
- Smoother operation
- Longer percentage of cycle spent at top-dead-center and bottom-dead-center for more complete combustion and exhaust scavenging
- Two power strokes for every rotation from the opposed pistons instead of one every other rotation (4-stroke) resulting in nearly twice the power at a given engine speed
- High compression and temperatures to cause an instantaneous and adiabatic reaction as opposed to a drawn out combustion
- Lean fuel/air mixture combined with the adiabatic reaction resulting in zero unburnt hydrocarbons in the exhaust
- Sealed underside of the piston to isolate the fuel/air mixture from the crankcase
- Eliminate the need to mix oil with the fuel as with standard 2-cycle engines
- Prevents the piston ring blow by from polluting the crankcase oil extending the life of the oil
Simplified explanation:
The Bourke engine should be considered an "explosion" engine because of the extremely fast burn time of the fuel air mixture.
The rising piston compresses the mixture heating it, because of the cool piston head and cylinder walls the mixture is not heated enough to start a burn. The piston "latches" at top dead center do to the action of the scotch yoke. Spark plug fires causing an explosive burn. All of fuel is burned completely because of explosive burn time. Sharp rise in pressure causes scotch yoke to "unlatch" piston. Piston moves down cylinder, expanding gasses following piston cause cooling of piston and cylinder walls. Since all of fuel was burned during "latching" of piston no fuel is being burned at this time, no heat is being added, all expansion results in cooling. When piston reaches the bottom of the cylynder it again "latches" until "unlatched" by the explosion in the opposite cylynder. This gives time for scavaging of explosive gases.
The mixture must be lean enough so that compression heating of the mixture does not cause it to ignite prior to the "latching". If this occurs engine will not run, or will run rough. Mixture of the fuel must be in the "explosive" range for the engine to run correctly.
The maximum pressure on the piston occurs right after the release of the piston from top dead center. It is not spread over the whole length of the piston travel as in a conventional engine. For this reason this is an extremely high torque engine.
The complete burn of the fuel while the piston is "latched" gives this engine its high efficiency and low emmissions.
The cooling caused by the expanding gases, behind the piston head and the non burning of fuel while piston is traveling, causes the low temperature exaust gases. This also prevents dieseling during the next compression cycle, because of the cooling of the piston head.
External links
- Bourke Engine Blueprints - Documentary - Bourke Engine Runs DVD Video - VLB Engine - Bourke Engines For Sale - Bourke 400 Blueprints - Vaux Engine - DeVaux Engine - RadCam Engine - ECO Engine And More!
- Commercial Bourke Engine development
- Bourke engine videos.
- Bourke Engine Project, LLC
- The Bourke Engine