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#111
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mastic wrote:
1. Desiel injection timing is differant than on an Otto engine. The fuel is injected during the intake cycle on the Otto engine and the fuel is injected during the ignition cycle on the Desiel. An Otto engine is any four stroke engine, diesel, gasoline, LPG makes no difference. And there is no "ignition" stroke. BTW, it is not ignition, or intake, or combustion "cycle". There is only one cycle in either a four stroke cycle or two stroke cycle engine. What is different is the number of strokes in a cycle. Cycle means repeating operation. A two-stroke cycle engine repeats its operation every two strokes, a four-stroke repeats every four strokes. I believe if we must shorten the terms then four-stroke and two-stroke are better terms, because in both cases we are talking about what happens in one cycle, not in two or four CYCLEs. |
#112
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Sport Pilot wrote:
mastic wrote: Bryan Martin wrote: Not so. In the Otto cycle, the fuel and air are introduced to the cylinder during the intake stroke. In the Diesel cycle only the air is introduce to the cylinder during the intake stroke, the fuel in injected at the end of the compression stroke. Wrong. Mr Otto invented the four stroke cycle and it is named after him. The fuel or when it's introduced has nothing to do with it, Otto refers to the cycle. SO? He didn't mention fuel in the part you snipped. Diesel is a differant cycle named after Mr. Diesel. Actually, today's Diesels can operate over several cycle types. Modern high speed Diesels as used in cars are closer to the Otto cycle than they are to Rudolph's cycle. In his original engine the fuel was supposed to be injected at a rate to create a constant combustion temperature or a constant pressure. This really would take a feedback of temperature or pressure during the combustion stroke, and was- and is- extremely hard to do. The slower the speed of the engine, the better current Diesels approach the intended Diesel cycle, as seen on an indicator diagram. The indicator diagram on high rpm Diesel auto engines look a lot like the diagram of an Otto cycle. There are people developing Diesel systems using closed loop pressure sensing to adjust fuel injection rate, but to my knowledge no Diesel car or truck engine using this feature has ever made it to production. Current production Diesels use open loop injection, so it is a hybrid cycle, somewhere between true Otto and true theoretical Diesel. |
#113
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mastic wrote: "MJC" wrote: "Andrew P." wrote in message link.net... Wandering aimlessly about the Web, I heard Sport Pilot say: You have most of it right. Some things you have wrong, 1. Desiel injection timing is differant than on an Otto engine. The fuel is injected during the intake cycle on the Otto engine and the fuel is injected during the ignition cycle on the Desiel. On the Desiel the fuel injection cycle starts just before TDC and ends well after TDC. The fuel ignites as soon as it hits the hot air. etc., etc. --- SNIP --- It's Diesel, not "Desiel". -- Andrew P. Well if you're going to get picky, it's "Auto" engine, not "Otto" engine. MJC Picky, picky, picky. It's not an Otto engine as such. Otto is used to refer to the standard four stroke cycle because Otto was good enough to invent the four stroke cycle. So our friend was incorrect when he said: 1. Desiel injection timing is differant than on an Otto engine. The fuel is injected during the intake cycle on the Otto engine and the fuel is injected during the ignition cycle on the Desiel. An Otto engine is any four stroke engine, diesel, gasoline, LPG makes no difference. Completely wrong, the Otto cycle has nothing to do with four stroke engines. Don is right its not four cycle, I used it incorrectly. The Otto and Diesel cycles are actually refering to the thermodynamics chart of temperature pressure and volume, they invented their cycles on paper and books, the engines we use are only close approximations. The two stroke ignition engine uses the Otto cycle as it is has the four phases of intake, compression, power, and exhaust, and the pressure is not constant. The Diesel two stroke is a Diesel cycle because it also includes the same phases and the fuel burns at a fairly constant pressure. |
#114
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Here is an animated link showing the differances of the Otto and Diesel
cycles. http://www.ulb.ac.be/sma/testcenter/...osedcycle.html Notice the near instant burning in the example gives very nearly a constant volume, in actual practice some compression is going on at this time. Also during a Diesel cycle it is hard to maintain a constant pressure, it would actually drop off, especially near the end of the down stroke. |
#115
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Sport Pilot wrote:
Completely wrong, the Otto cycle has nothing to do with four stroke engines. Don is right its not four cycle, I used it incorrectly. The Otto and Diesel cycles are actually refering to the thermodynamics chart of temperature pressure and volume, they invented their cycles on paper and books, the engines we use are only close approximations. The two stroke ignition engine uses the Otto cycle as it is has the four phases of intake, compression, power, and exhaust, and the pressure is not constant. The Diesel two stroke is a Diesel cycle because it also includes the same phases and the fuel burns at a fairly constant pressure. I guess I'd quibble with the statement that the Otto cycle has nothing to do with four-stroke engines- it was the first successful cycle to incorporate four strokes. yes, there are other four stroke cycles, but the Otto cycle is still by far the most common. There have been several other four-strokes, several two-strokes, at least on six stroke- I suspect several also. New IC engine designs are among the most numerous US patents. Just because something is patentable, of course, does not make it good or successful, and most of these patents were for approaches that offered insufficient advantages. BTW, as I understand the new Miller cycle, I don't consider it a truly new cycle- just a clever mod on the Otto. I don't consider the Otto cycle to require valve openings at closings at the top or bottom dead center, exactly. |
#116
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Don Stauffer wrote: Sport Pilot wrote: Completely wrong, the Otto cycle has nothing to do with four stroke engines. Don is right its not four cycle, I used it incorrectly. The Otto and Diesel cycles are actually refering to the thermodynamics chart of temperature pressure and volume, they invented their cycles on paper and books, the engines we use are only close approximations. The two stroke ignition engine uses the Otto cycle as it is has the four phases of intake, compression, power, and exhaust, and the pressure is not constant. The Diesel two stroke is a Diesel cycle because it also includes the same phases and the fuel burns at a fairly constant pressure. I guess I'd quibble with the statement that the Otto cycle has nothing to do with four-stroke engines- it was the first successful cycle to incorporate four strokes. yes, there are other four stroke cycles, but the Otto cycle is still by far the most common. There have been several other four-strokes, several two-strokes, at least on six stroke- I suspect several also. New IC engine designs are among the most numerous US patents. Just because something is patentable, of course, does not make it good or successful, and most of these patents were for approaches that offered insufficient advantages. BTW, as I understand the new Miller cycle, I don't consider it a truly new cycle- just a clever mod on the Otto. I don't consider the Otto cycle to require valve openings at closings at the top or bottom dead center, exactly. The confusion is that Otto invented the first four stroke engine and called it the Otto cycle, not because of thermodynamics but because he put it in a motorcycle. However the thermodynamic cycle can be reproduced with a two stroke engine. Its just that the intake and exhaust cycle's are much shorter. |
#117
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Sport Pilot wrote:
Don Stauffer wrote: Sport Pilot wrote: Completely wrong, the Otto cycle has nothing to do with four stroke engines. Don is right its not four cycle, I used it incorrectly. The Otto and Diesel cycles are actually refering to the thermodynamics chart of temperature pressure and volume, they invented their cycles on paper and books, the engines we use are only close approximations. The two stroke ignition engine uses the Otto cycle as it is has the four phases of intake, compression, power, and exhaust, and the pressure is not constant. The Diesel two stroke is a Diesel cycle because it also includes the same phases and the fuel burns at a fairly constant pressure. I guess I'd quibble with the statement that the Otto cycle has nothing to do with four-stroke engines- it was the first successful cycle to incorporate four strokes. yes, there are other four stroke cycles, but the Otto cycle is still by far the most common. There have been several other four-strokes, several two-strokes, at least on six stroke- I suspect several also. New IC engine designs are among the most numerous US patents. Just because something is patentable, of course, does not make it good or successful, and most of these patents were for approaches that offered insufficient advantages. BTW, as I understand the new Miller cycle, I don't consider it a truly new cycle- just a clever mod on the Otto. I don't consider the Otto cycle to require valve openings at closings at the top or bottom dead center, exactly. The confusion is that Otto invented the first four stroke engine and called it the Otto cycle, not because of thermodynamics but because he put it in a motorcycle. However the thermodynamic cycle can be reproduced with a two stroke engine. Its just that the intake and exhaust cycle's are much shorter. I am not sure what you mean by exhaust and intake "cycles". There is one cycle- the actions that the engine goes through before everything repeats. Do you mean the portions of the cycle during which the exhaust and intake take place- they definitely take less crankcase revolution angle. In the Otto cycle it is easy to break it down into four operations, each lasting one stroke. A two-stroke is more complicated, because it still has (existing, contemporary ones, do anyway) four seperate functions of intake, compression, combustion and exhaust, but have to do it in two strokes. |
#118
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Don Stauffer wrote: Sport Pilot wrote: Don Stauffer wrote: Sport Pilot wrote: Completely wrong, the Otto cycle has nothing to do with four stroke engines. Don is right its not four cycle, I used it incorrectly. The Otto and Diesel cycles are actually refering to the thermodynamics chart of temperature pressure and volume, they invented their cycles on paper and books, the engines we use are only close approximations. The two stroke ignition engine uses the Otto cycle as it is has the four phases of intake, compression, power, and exhaust, and the pressure is not constant. The Diesel two stroke is a Diesel cycle because it also includes the same phases and the fuel burns at a fairly constant pressure. I guess I'd quibble with the statement that the Otto cycle has nothing to do with four-stroke engines- it was the first successful cycle to incorporate four strokes. yes, there are other four stroke cycles, but the Otto cycle is still by far the most common. There have been several other four-strokes, several two-strokes, at least on six stroke- I suspect several also. New IC engine designs are among the most numerous US patents. Just because something is patentable, of course, does not make it good or successful, and most of these patents were for approaches that offered insufficient advantages. BTW, as I understand the new Miller cycle, I don't consider it a truly new cycle- just a clever mod on the Otto. I don't consider the Otto cycle to require valve openings at closings at the top or bottom dead center, exactly. The confusion is that Otto invented the first four stroke engine and called it the Otto cycle, not because of thermodynamics but because he put it in a motorcycle. However the thermodynamic cycle can be reproduced with a two stroke engine. Its just that the intake and exhaust cycle's are much shorter. I am not sure what you mean by exhaust and intake "cycles". There is one cycle- the actions that the engine goes through before everything repeats. Do you mean the portions of the cycle during which the exhaust and intake take place- they definitely take less crankcase revolution angle. In the Otto cycle it is easy to break it down into four operations, each lasting one stroke. A two-stroke is more complicated, because it still has (existing, contemporary ones, do anyway) four seperate functions of intake, compression, combustion and exhaust, but have to do it in two strokes. Sorry for the confusion, the two stroke doesn't take a stroke for those functions so I used cycle, can't think of anything else to call it. |
#119
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"Don Stauffer" wrote A two-stroke is more complicated, because it still has (existing, contemporary ones, do anyway) four seperate functions of intake, compression, combustion and exhaust, but have to do it in two strokes. And some of the operations are happening simultaneously. |
#120
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"Morgans" wrote in message news "Don Stauffer" wrote A two-stroke is more complicated, because it still has (existing, contemporary ones, do anyway) four seperate functions of intake, compression, combustion and exhaust, but have to do it in two strokes. And some of the operations are happening simultaneously. There is one very efficient 2-stroke variant that does have separate and distinct intake, compression, combustion and exhaust functions - the opposed-piston 2-stroke diesel with the pistons driven by cams, not crankshafts. As the pistons move apart (power), the exhaust port is uncovered first by one piston (exhaust) and then the intake is opened by the other piston so high pressure air from the supercharger can scavenge the last bits of exhaust gas from the space between the pistons. After the cylinder is scavenged, the first piston closes the exhaust port leaving the intake port open so the supercharger can charge the cylinder with air (intake). Then both pistons move together closing the intake port (compression). Fuel is injected directly into the space between the pistons which forms a spherical combustion chamber (ignition). The cams are designed to optimize the timing and duration of the port openings as well as contour the compression and power strokes. This design makes extreme demands on metallurgy and lubricants so is just now becoming practical. Bill Daniels |
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