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Been working on a new engine design

  1. Dec 13, 2009 #1
    So, i've been working on an engine design that has been tried already, and nobody has really got it to work the way i think that it should. The engine i'm working with is a Wankel Rotary Engine and what i'm trying to do is make a modern, high-efficiency, high power-output diesel out of it. I'm not the first to try this, and there are diesel rotary's out there, but they don't use high compression, compression ignition or a high pressure direct injection system. There is a reason why, it's a physics problem with flow through the combustion chamber. When the compression is raised too high, the passage separating the two halves of the combustion chamber becomes too small and the volume of energy cannot pass through, creating two separate combustions chambers, driving against each other. i am looking for some help from some guys that are smarter than i am, basically. Here is a link to a video for anyone who wants to see the basics of how the engine works if you don't know, and please pm me, anybody, with any input, or info on the idea. i'll fill you in more on what my plans and ideas are already. i have an engine already torn down to start development of this. There is a HUGE amount of potential in this engine with diesel power. i think it could replace a lot of 4, 6 and possibly 8 cylinder engines, while running on biodiesel, veg. oil, or many other products. Please just PM me here or post on this thread, i wanna get some input from some guys in the physics world. thanks in advance for any help you guys may be able to offer!

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  3. Dec 13, 2009 #2


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  4. Dec 13, 2009 #3


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    IIRC one of the major issues was the material for the tip seal. These seals undergo continuous hi speed contact with the chamber walls. So it is very difficult to maintain the high compression needed.
  5. Dec 13, 2009 #4
    the problem is that peanut buldge in the middle of the epitrochoid housing . when you raise the compression you must fill in the bath tub on the rotor face. when you've filled it in far enough the leading and trailing (top and bottom) sides of the combustion chamber become separate chambers unable to efficiently flow between eachother and working directly agaist eachother. i need to come up with rotor face design the would allow a common combustion direction. i have a couple ideas i am going to try with injection timing.

    Last edited: Dec 13, 2009
  6. Dec 14, 2009 #5
    The favored approach is to improve on what's widely regarded as the most sophisticated engine technology available today: the LSX pushrod engines. If Chevrolet can generate more power from an engine that's compact and light enough to fit into an inline-4 engine bay (Corolla, etc), then any improvements on this amazing technology--especially improvments that involve diesel to the LSX engine--will stand to benefit from further gains. I wouldn't bother with Wankel engines.
  7. Dec 14, 2009 #6
    they don't make an lsx engine that makes more power or torque per liter than the renesis engine. plus, the three rotor face combustions per single eccentric shaft turn makes it more viable to diesel use and the difference in flame front speeds. more moving parts is always, ALWAYS less efficient, i don't care how lightweight you make them. and diesel would be harder to use in an engine that's ALL aluminum. But, i think someone should do it, personally, i am not a push rod guy. wasted energy is wasted energy, regardless of where it's wasted.
  8. Dec 14, 2009 #7
    You need to work with "commom rail" injection principles then you'll be aware that the injector 'pulses' through the combustion phase. This will overcome the inherent low torque available from reduced use of the piston cycle in single squirt direct applications. Modern high injectors are of the piezo variety and operate very quickly over a longer duration.
    With this is mind for a wankel application the key is to design an effectice combustion zone that directs the expanding pressure in the forward part of the cylinder ie in front of where the seal will pass the tdc point. (in the youtube reference you gave it would be tantamount to mounting the injector where the lower of the two sparkplugs are.)
    The most effective way is to form the combustion dish into two seperate bowls with perpendicular sides. (a transfer between the two is necessary but more later) Imagine two bath plugs places next to each other with the hollows uppermost. In the engine itself, plug (or pot) 1 leads pot 2.
    Now remembering that a piezo injector for maximum efficiency in a diesel will fire aproximately at top dead centre, have the injector placed to fire directly into pot 1. This will case a flame front to cause a pressure front that will travel against the combustion chamber side-wall. The injector phase will finish opposite number 2 pot.
    A transfer chamber that looks cross-sectionally like a piece of gutter between the two pot combustion chambers will serve to ensure the flame front on initial firing loses pressure rapidly as it travels into number 2 pot. (the flame front and maximum pressure transfer will be constant (effectively bearing onto the side-wall in the combustion chamber side). If you calculate the swept volumes effectively for the approx overall compression in the 17.5 to 1 plus ratio, maximum pressure will always be sufficiently generated in the combustion side of the casing to ensure even torque loading.
    Theoretically and to increase swirl and limit pressure spots an exhaust transfer port bleeding exhaust air into the compression side of the case just forward of tdc will help raise the air temperature and enable compression to be lowered for better fuel and power transfer efficiency. There is no reason why the transfer port cannot be of a valve arrangement enabling a glowplug (cold start) to be placed in the port. Air being pushed out of the exhaust outlet is forced through the transfer port heated by the glow plug before entering the compression side of the crankchamber.
    Hope I've made it clear enough. If not let me know on post back and I'll drop you a drawing.
    Critical measurement will be "pot depth" against distance from the pot bottom to the combustion chamber side wall as a ratio against the tranfer tube cross-sectional area between pots 1 and 2. Get this right and it will ensure even combustion pressure through the flame-cycle phase. You may need to get an engineer to map it on a computer for you.
    Because piezo injectors are electrically operated, the engine management system will ensure effective injector firing timing to avoid injection into the transfer port between the 2 pots.
    There is a massive amount of fine tuning that can be done with this especially exhaust gas re-cirulation and turbo for a very green output. The fuel you go for will be critical to avoid gumming of the cylinder walls and seal degredation as a result.
    Notching of the seals could be feasible as a facilitator to raising the air temperature on the inlet side, The other thing worth considering is having the seals free to move held in a three-quarter cup with a positive oil pressure system adding lubrication. This will prolong the seals for the high-pressure application and reduce frictional wear. Diesel fuel is a heavier oily grade anyway so this tiny bit extra wont hurt.
    Good luck with your project.
  9. Dec 14, 2009 #8
    i was thinking the same thing with injectors, using a high pressure common-rail setup in the position of the lower spark plug hole, and using i believe it's up to 8 injector pulses per comb. process, through to the trailing edge of our bathtub. I am also wondering if possibly moving the bathtub closer to the leading edge of the rotor edge and advancing injector pulse would increase leverage on the eccentric shaft to create even better torque numbers. Delphi makes an aftermarket common rail injection system if you want to check it out, that's what i'm planning to use. Other problems i will have is in the separation of the housings themselves and in wear internally as well as the more violent (detonating) nature of the diesel fuel. The seals in the earlier engine are thicker than later engines and much stronger, and i am working with a friend at a ceramics company right now to choose the right coating, but what i want to do is coat the seals, rotors, and housings. This is already common practice on race engines, and with her help i think i can find a coating that can give the rotary at least a couple hundred thousand miles expected use, but i think if coated properly, i'm going to try and make a 500,000 mile engine...but that's definitely second to performance, so we'll see. thanks for all inputs, responses and replies.
  10. Dec 21, 2009 #9
    HI. I'm new to this forum (or ANY forum) but I couldn't help overhearing your conversation. Although now retired, I am on the Board of a company called Patrick Power Products, Inc. "PatPower" manufactures a line of rotary (Wankel) diesel engines. These engines are sold primarily to DoD (Army, Navy and USMC) and several Defense Contractors. The engines are very small, and used for auxillary power (APU) generation, and not for prime-moving power. At PatPower we have indeed converted larger engines to diesel, such as the Mazda engine, but the drop in BHP output does not make it a winner. I can answer any questions directly at Jack@Thornhedge.com[/U], or I still read my Company email occasionally at JFrost@PatPower.com. Cheers.
  11. Dec 30, 2009 #10
    what compression ratio are you running? mazda had already done a lot of testing with compression ratio and combustion chamber design and so, we already know that above 12:1 compression, the bhp begins to drop WAY off because of a lack of airflow through the combustion phase of the engine's rotation. That is why i was trying to make a couple of drastic changes in design. I'd love to hear more about the engines you guys use. i've seen other diesel rotarys out there, there is a german company that make some really badass ones, but the power output is nowhere near what the engine should be capable of.
  12. Jan 7, 2010 #11
    Compression ratio is in the range of 11:1 to 12:1. The engines manufactured by the Company are not true diesels in that they are not totally compression-detonated. However, they do burn JP-8 (basically kerosene/diesel fuel) which is a military requirement. Gasoline is not practical for military fuel, it is considered to hazardous.
  13. Jan 9, 2010 #12
    the engine i want to build is a true diesel, compression ignited. and it's very important that it does work this way. there are several companies world-wide that make spark and heat ignition diesel engines. some even have their own housing designs and things. i don't understand why they don't work harder to create a true compression diesel if they are designing housings and things from scratch. i understood why mazda didn't. they already had a design to work with, and it worked really well with all the gasoline engines they used. if you are interested in working with me on getting an actual engine built, i'd love to work with a group that has a means of creating it. i personally don't have the resources to build it the way i have designed it.
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