Crower six stroke
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This article contains information about scheduled or expected Category:Proposed engine designs. It may contain preliminary or speculative information, and may not reflect the final specification of the product. |
The Crower six-stroke engine is a concept under development by Bruce Crower.
Two extra strokes are added to the customary internal combustion engine four stroke Otto cycle, which makes a Six stroke engine. A third down-stroke is a "steam stroke" and a third up-stroke exhausts the expanded steam while venting heat from the engine.
The engine cold starts on the Otto cycle, coasting through the fifth and sixth strokes for a short period. After the combustion chamber temperature reaches approximately 400 degrees Fahrenheit (200 °C), a mechanical operation phases in the fifth and sixth cycles. Just prior to the fifth-cycle, water is injected directly into the heated combustion chamber via the converted diesel engine's fuel injector pump, creating steam and another power stroke. The phase change from liquid to steam removes the excess heat of the combustion stroke forcing the piston down (a second power stroke). As a substantial portion of engine heat now leaves the cylinder in the form of steam, no cooling system radiator is required. Energy that is dissipated in conventional arrangements by the radiation cooling system has been converted into additional power strokes.
In Crower's prototype, the water for the steam cycle is consumed at a rate approximately equal to that of the fuel, but in production models, the steam will be recaptured in a condenser for re-use. Heat will be available from the condenser to provide interior heating of the vehicle, much as a conventional heater core works in cars and trucks today.
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[edit] Positive aspects:
Crower claims a 40% reduction in fuel consumption and reduced exhaust emissions per a given power range.[1]
The principle advantage present in the six-stroke design is the engine's ability to extract work from heat that is otherwise lost through the cooling system of a conventional four-stroke engine. Since the steam strokes have the side-effect of cooling the engine internally , this will allow the use of much higher compression ratios, allowing the full potential of a fuel to be extracted. Since heat that previously would have been drawn out of the engine via the cooling system can be harnessed, compression ratios once useable for only short term applications (such as race engines) could conceivably be used in regular, long-running time scenarios without environmentally harmful anti-knock chemicals. Ultra-lean air/fuel mixtures, desirable for low emissions and high efficiency, may be used since excess heat, undesirable in other engine architectures, can likewise be harnessed in six-stroke applications. Under these circumstances, far more energy from fuel could be converted to horsepower output.
The weight and power loss of most conventional cooling system parts, such as the fan, radiator and coolant pump can be eliminated. On a large diesel truck, these parts may weigh as much as a thousand pounds.
The mechanical modifications needed to "six-stroke" a small air-cooled industrial diesel already being manufactured are far less complicated than any hybrid system. Many maintenance features of this engine would be parallel or identical to the knowledge base of mechanics well-versed with gasoline, diesel, and racing engines.
Physical engine size reduction (per a designated power rating) is possible as one-third of the engine strokes produce power (in the Crower six-stroke), instead of one-quarter (in the Otto cycle). This, coupled with the fact that the extra power stroke is provided by using water instead of fuel means there is a significant improvement to the fuel efficiency and pollution per a given power range, and this is in a field where small improvements create great interest.
The higher percentage of power strokes may allow lower operational speeds, with higher torque output at lower and broader rpm ranges. Lower operational speed might allow designs with greater crankshaft diameter, for the use of engine dimensions with inherently more torque potential.
This is the only high pressure steam engine that does not require a certified pressure boiler and related hardware complexities, dangers, and weight penalties.[citation needed]
[edit] Obstacles or problems:
A warm up period would be required in all automotive applications. Power and efficiency (!) is reduced during the warm-up period.
A steam-free cool down period is required to clear water/steam from the engine.
Cold climate anti-freezing measures would be required in the water reservoir.
Oil adulteration, from the water/steam cycle, is an obstacle to be dealt with, though additional piston/cylinder sealing rings can be easily added and special oils used. Also, data from lube oil engineering systems for steam turbines is readily available to help identify likely concerns and possible "well-researched" remedies.
The weight of an oil separator and a water condenser are likely additions, although these will be far smaller and lighter than a conventional cooling system.
Endurance testing will likely identify components that may need to have upgraded materials designated, such as possibly using stainless steel for the valves, cylinders, and rings.
Prior art exist to Mr. Crower's invention, but no preexisting six-stroke patents were mentioned in his patent application. [2] [3] As of May 2008, no patent has been awarded.
[edit] Possible engine configurations and applications
It should be noted that the Crower six-stroke is not the same technology as water injection, where water is added to the incoming air/fuel mixture to allow higher power output through internal cooling.
The "steam" power stroke and the "burning hydrocarbon" stroke may not produce the same amount of force as each other. A one-cylinder engine would run much smoother with a relatively heavy flywheel to smooth pulsations, much like the early large one-cylinder diesel industrial factory engines.
One down-stroke does not provide any power, and the other two down-strokes may each provide slightly different levels of power. This suggests the most compact configuration that will provide an inherently smooth running operation is an in-line three-cylinder engine. Of course, many other configurations and cylinder quantities can be made to work.
Although the Crower cycle could be made functional with a variety of fuels and RPM ranges, steam theory suggests it would be very useful when coupled with a diesel cycle, which performs well in low-rpm long-stroke applications.
A Crower cycle engine may eventually prove to be useful as a passenger vehicle power plant, but even if its implementation in that field proves troublesome, there are several less-regulated fields in which it should prove to be immediately successful, including transport diesel trucks, heavy equipment (bulldozers, etc), buses, and stationary power generators, among others.[citation needed]
A large number of municipalities are beginning to generate electricity by burning the methane gas that is emitted by the decaying trash in landfills. Doing this consumes a greenhouse gas, and reduces the amount of electricity that needs to be produced by burning coal. This type of methane is often described as too "wet" and "dirty" to burn in the preferred gas turbine generator, so it is often burned in large V-12 locomotive diesel engines that have had a sparking system added. The Crower Cycle would improve the fuel consumption and emissions per a given amount of power generated, which is significant considering today's stringent environmental concerns over increasing electrical generation needs.[citation needed]
[edit] Related US Patents
1339176 Internal combustion engine May 4, 1920. Leonard H. Dyer invented the first 6-stroke internal combustion/water-injection engine in 1915.
3964263 Six cycle combustion and fluid vaporization engine Jun 22, 1976
4301655 Combination internal combustion and steam engine Nov 24, 1981
4433548 Combination internal combustion and steam engine Feb 28, 1984
4489558 Compound internal combustion engine and method for its use Dec 25, 1984
4489560 Compound internal combustion engine and method for its use Dec 25, 1984
4736715 Engine with a six-stroke cycle, variable compression ratio, and constant stroke Apr 12, 1988
4917054 Six-stroke internal combustion engine Apr 17, 1990
4924823 Six stroke internal combustion engine May 15, 1990
6253745 Multiple stroke engine having fuel and vapor charges Jul 3, 2001
6311651 Computer controlled six stroke internal combustion engine and its method of operation Nov 6, 2001
6571749 Computer controlled six stroke cycle internal combustion engine and its method of operation Jun 3, 2003
7021272 Computer controlled multi-stroke cycle power generating assembly and method of operation Apr 4, 2006
[edit] References
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