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Tricylinder Supercombustion

Compression ignition
  [vote for,

Well as some have already proposed and mentioned here, boiling gasoline and then injecting it into the cylinder could potentially reduce emissions, allow for a leaner mixture, and make it basically compression ignition with no need for spark plugs. The only problem is how to do this well.

Not surprisingly, something like the Crower Cycle came to mind when I thought about this. The only problem was how to prevent the gaseous gasoline from mixing with air too soon and causing preignition.

Meet the Tricylinder Supercombustion engine. It works on a design similar to that of a Scuderi engine. The cylinder count can only be increased by groups of 3, and each group has two combustion cylinders on each side and one compressor cylinder in the middle. In a Scuderi engine (which uses groups of 2 cylinders and not 3), when the compression cylinder is sucking in air the combustion cylinder is combusting. When it is compressing air the other is exhausting. I propose adding an extra stroke to each combustor cylinder by injecting gasoline after the exhaust valve has closed. It will immediately turn to gas and expand, yielding some extra power. Then once it compresses the gas to the top, the compressor cylinder's charge gets expelled into the combustion cylinder, and the mixture immediately ignites.

Now the power cylinders are setup so that they are producing power at different times. When one is having a gasoline expansion cycle, the other is combusting. This way the compressor cylinder is always being used to the fullest. The heads on each cylinder are 4 valve heads. For the combustion cylinders this means 2 intake valves and 2 exhaust. For the compressor cylinder it means 2 into the left combustion cylinder and 2 into the right. There is an extra valve (sleeve valve) in the compressor cylinder for it to intake air.

At low RPMs when the engine isn't yet warm enough to vaporize the gasoline, the expansion cycle is skipped (with the exhaust valves closed to prevent pumping losses) and injectors/sparkplugs temporarily control the combustion cylinders until they're up to opperating temperature. The benefits of this seem pretty good. Increased fuel economy, no need for sparkplugs, as high a compression ratio as desired, better combustion, waste heat recovery, and finally (although there could be more) most likely no need for a cooling system.

acurafan07, Sep 01 2007

Scuderi Design http://www.scuderig...the_technology.html
Scroll down to the 4th picture [acurafan07, Sep 01 2007]


       Hello, just wondering when you put --"Then once it compresses the gas to the top, the compressor cylinder's charge gets expelled into the combustion cylinder, and the mixture immediately ignites."-- How do you seperate the two chambers? that is would the burning mix not overpower your compressor?
the dog's breakfast, Sep 01 2007

       Sorry, I'll try to find a link to the Scuderi Engine. It's design will explain what I mean. It uses two different cylinders, one slightly advanced in its cycle than the other, for the different purposes. Once the compressor and combustion cylinder have reached the top, valves open and the gas from the compressor cylinder flow into the combustion cylinder. Then the valves in both immediately close to prevent leakage.
acurafan07, Sep 01 2007

       [acurafan07] Maybe you should change your name to [one_engine_per_day_07] :)   

       Your mind is very fruitful.   

       [+] for anything to do with alternative fuel(ing) ideas.
Giblet, Sep 01 2007

       Thanks [Giblet]. As to alternative fuels, this could probably be used with almost anything (including biodiesel) that is a liquid and can be combusted.   

       I just wouldn't try it with Nitromethane since it supplies its own oxygen. Inject it into the combustion cylinder as an expansion stroke and you've immediately just added an extra combustion stroke.
acurafan07, Sep 01 2007

       So you're using the heat left in the engine to expand liquid gasoline into a vapor, then compressing it and burning it? I'm not really sure why you would need sets of three cylinders for this, or if the gasoline would even expand enough to make any kind of difference, since you're compressing it again.
discontinuuity, Sep 01 2007

       The 3 cylinders is because otherwise the compressor cylinder would go through one waste cycle. With only two cylinders, with the combustion cycle the compressor cylinder would be intaking, then with the exhaust compressing. If you then added the expansion and compression to the power cylinder, the compressor cylinder would have to go back down and up again. With 3-cylinders the cycles would happen at different times so that when one cylinder goes through expansion the other goes through combustion.   

       The expansion isn't really to add much power, just for the benefits listed above.
acurafan07, Sep 01 2007

       Thanks, nice link. See what you mean now thanks!
the dog's breakfast, Sep 02 2007

       //I just wouldn't try it with Nitromethane since it supplies its own oxygen. //   

       That comment gets me thinking...
Let's suppose we reverse the whole thing and compress gasoline vapour with no oxygen. Then inject some Nitro-methane...
Ling, Sep 03 2007

       Lol, you'd probably end up with such an extremely rich mixture that the exhaust would look as if it was comming from a gas turbine. Even in drag racing engines designed to run on nitromethane (and supercharged air), the nitromethane isn't finished burning in the combustion chamber and shoots flames out the exhaust. That would be neat though.
acurafan07, Sep 03 2007

       I like pictures! I had to read this a 20 times to understand what your saying...   

       You made up for your magnetic piston idea. But you would have to use sparkplugs. If you try to auto ignite you will losses too much power through the compressor to combuster connector. As soon as the first drop of gas gets mixed with the compressed air it will ignite meaning that there will not be enough time to get all the air to get inside the combustion chamber before you lose most the power potential. If you had spark plugs you could control when the air/fuel ignited. Then you would have a Scuderi engine with a gas Crower cycle and that might work.
F_R_O_G, Sep 03 2007

       I'm confident you could advance the compressor cylinder such that the combustion wouldn't be a problem. There wouldn't be any other way to do this, however, since once the gaseous fuel comes into contact with air it's as good as combusted.   

       As to the magnetic valves idea (not pistons), I thought of a way for it to work just fine, however there would simply be no benefits. But thank's for the redemption part, I take that as a compliment.   

       As to the fact that there's no picture, I wish I could have made one, but I'm not exactly a photoshop wizard. Every computer illustration I've ever done completely myself had been made on Microsoft Paint. To explain anything about this idea in an illustration I personally could do would probably take hours. I felt a good description would have to be suficient. But I too like pictures.
acurafan07, Sep 03 2007

       How are you picturing the airflow? like "the dog's breakfast" said the combustion would overpower the compressor. You couldn't get all the air into the combustion chamber before it ignited unless you want to make the engine knock. The compressor advance will only put the air in before full compression then when compression in the combustion chamber gets higher the mixture will explode.   

       You could have the compressor chamber be thinner so that it would be impossible to overpower it. I don't know how effective that would be though.   

       Didn't you see my professional looking pictures with the 8stroke engine?
F_R_O_G, Sep 06 2007

       [F_R_O_G], if the boiled part was only true at high rpms, there would be so little time for combustion backpressure that it might as well not be a factor. If worse comes to worse, the crossover passage could always hold all of the compressed air and have the compressor cylinder's valves close. Sure it would add extra volume to the combustor cylinder, but as long as the compressor cylinder is much larger (to create a supercharging effect) that wouldn't matter either.   

       And yes I did see your pictures. See my idea for a Gas Turbine Wankel for a picture I put on here once. I didn't mean that a picture for this can't be done just that I don't have the time.
acurafan07, Sep 06 2007


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