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Thread: Smallest model true diesel?

  1. #41
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    ..or just propane. Plenty of diesels running on that and natural gas.

  2. #42
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    Quote Originally Posted by lakeside53 View Post
    ..or just propane. Plenty of diesels running on that and natural gas.
    The diesel or compression ignition engines that I'm aware of that use those gases commercially are either dual fuel engines that use diesel to initiate the burn so that diesel is first added as a pilot injection in order to start the gas burn or they are spark ignited high compression gas engines. Natural gas and lpg both have low cetane index numbers and auto ignition temperatures are much higher than conventional diesel fuel.

    The dual fuel pilot injection engines do have some advantages and also a lot of complications due to the very nature of running varying ratios of the two fuels in order to take full advantage of either fuel under various operating conditions. This is probably the big deterrent to their popularity. High compression spark ignited engines are very popular where natural gas is the primary fuel source and of coarse where it can be plumbed in due to the storage limitation issue inherent with natural gas.
    It takes a very high pressure tank and it's associated infrastructure in order to come close to duplicating the range commonly available in mobile applications. However some inroads have been made recently that enable their use in regional applications but they still command a relatively high entry fee to get started.
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  3. #43
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    Interesting. Something else learned today! We use them for 40 to 250kw generators. now I'm wondering what they are... or if someone is BS'ing me. There is no dual fuel for sure. The propane tank are just "ordinary" 500-1000 gallon tanks. Our 600kw is straight diesel. I'll have to pull the covers next time I'm on site look at the engines. Never have seen maintenance a bill for spark plugs though.
    Last edited by lakeside53; 12-23-2018 at 02:36 AM.

  4. #44
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    I'd be very surprised if they weren't spark ignited, I haven't seen one that wasn't.
    As mentioned common gaseous fuels have a very high auto ignition temperature requirement and a low cetane index number, not very conducive to compression ignition. They do however posses a very high natural octane number making them ideal fuels in very high compression spark ignited engines. This allows them to have a very high thermal efficiency.

    Here's a couple of PDFs that point out the spark ignition requirement of a couple of these engines. I think you'll find they all share this trait.

    https://www.energy.gov/sites/prod/fi...%20Engines.pdf

    https://www.energy.gov/sites/prod/fi...yford-pike.pdf
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  5. #45
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    Quote Originally Posted by QSIMDO View Post
    Problem with miniaturizing a true injected diesel single cylinder is the engine can't generate enough power to keep the flywheel going when you reach enough compression to ignite and conversely, make the rotating mass smaller then the compression can't be made high enough.
    I remember that's what the Navy told me 52 years ago in Engineman A school.

    How about 3d printing one in titanium? The piston doesn't need to be solid as it would be when done by subtractive methods.

  6. #46
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    Find Hansen is using kerosene in the 20mm diameter cylinder units.

    You really should look at his build video that I linked to above, if you have not. (some comments question the capability to do things that his engines do already)

    He shows his injector, partly assembled and taken apart. It is a simple pintle type injector.... "simple" in that there are few parts, but not in the research he did to develop it.

    He also shows the spray pattern, from several angles, with the injector on his test stand.

    While he HAS used other fuels such as turpentine in the semi-diesels, he IS using kerosene (paraffin) in these true diesels. Look at the video, it is not too long, and he really gives some good information. Obviously he does not need to heat the fuel, nor add an igniter fuel component, etc. He runs it as a diesel on diesel fuel. He can cold start the engines. ("Cold" does not include -40C, many full size diesels are hard to start below maybe 10C)

    I would imagine he filters the fuel, but...
    Last edited by J Tiers; 12-23-2018 at 04:05 AM.
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  7. #47
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    I've never seen a miniature diesel. Smallest one I ever saw was on a lawn tractor, maybe 20 hp. It was a twin cyl.
    I didn't think that they made miniature models.
    My question here is given the compression ratios of diesels how do they get their momentum to over come the compression stroke on a miniature?
    A big heavy fly wheel? With out it I can't see where there is enough internal mass.

    JL..............

  8. #48
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    Quote Originally Posted by J Tiers View Post
    Find Hansen is using kerosene in the 20mm diameter cylinder units.

    You really should look at his build video that I linked to above, if you have not. (some comments question the capability to do things that his engines do already)

    He shows his injector, partly assembled and taken apart. It is a simple pintle type injector.... "simple" in that there are few parts, but not in the research he did to develop it.

    He also shows the spray pattern, from several angles, with the injector on his test stand.

    While he HAS used other fuels such as turpentine in the semi-diesels, he IS using kerosene (paraffin) in these true diesels. Look at the video, it is not too long, and he really gives some good information. Obviously he does not need to heat the fuel, nor add an igniter fuel component, etc. He runs it as a diesel on diesel fuel. He can cold start the engines. ("Cold" does not include -40C, many full size diesels are hard to start below maybe 10C)

    I would imagine he filters the fuel, but...
    I have looked at the video and am amazed at what he has done and accomplished and am not questioning his abilities or techniques, on the contrary.

    Diesel fuels vary to a greater or lessor extent in their cetane index considerably depending on the source of the crude oil they are refined from as well as the refinery from which they come. It is also common practice to add a cetane index improver at the refinery in order to bring a given fuel up to a set standard.

    My suggestion that he use an additive to improve the fuel's ability to auto ignite using a common over the counter cetane index improver in addition to the kerosene he is using now is just another tool for him to take advantage of. Just as the kerosene itself lowers the auto ignition temperature requirements in comparison to diesel fuel, just another tool to take advantage of, no different than keeping his cylinder head uncooled. You have to grab the fruit where you can.
    Who knows, perhaps he is doing so already without mentioning it, he has certainly used all of the tricks I can think of to make things work.
    I congratulate him for his success and perseverance.

    Just as a point of reference, a 32 oz. bottle treats 250 gal. just because a little is good doesn't mean a lot is better.



    https://fppf.com/product/8-cetane-improver/

    Increase Cetane Increase Efficiency Diesel engines function on the principle of Auto Ignition. The proper diesel fuel cetane number is critical to maximize engine performance. At present most diesel fuels have a cetane number considerably below the optimal for best engine performance. 8+ Cetane Improver will significantly raise cetane levels of your diesel fuel. This product is the most powerful cetane improver on the market today.
    FPPF 8+ Cetane Improver provides:

    • Faster starting
    • Reduced smoke and emissions
    • Greater engine efficiencies
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    • Increased fuel mileage
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