4-stroke diesel

Discussion in 'Diesel Engines' started by Lemans, Feb 17, 2016.

  1. Lemans
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    Lemans Lemans

    Yes, a set-up as shown in the drawing (without one-way valves) is for one ore an undefined number of isolated cylinders only.
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    FAST FRED Senior Member

    Would not simple reed valves (OTS from an outboard) work as your one way valve?
  3. DCockey
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    DCockey Senior Member

    What advantage does this design offer compared to a conventional four stroke? This is mention of "higher volumetric efficiency" - does this mean more air in the cylinder? Is the claim more power for the same displacement? Any estimates of the power needed to move the air through the crankcase? Will the specific fuel consumption increase or decrease?
  4. Lemans
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    Lemans Lemans

    Yes, I can't rule out that simple reed valves can do the job.
    The picture shows the crank-case of a flat 2 prototype. You can see the holes where we have mounted reed valves. 2 allowing the air into the crank-case, 2 connected with an air-box.
    Although the position and form of these valves were not ideal and piston/crank/connecting rod came from a stock engine, we had 1.8 bar air-box pressure.
    In a new prototype, new high speed reed valves are used and these are mounted, no longer in the center of he crank but just under the piston.
    The power needed to compress the air was 0.5 HP for a 600cc engine.

    Attached Files:

  5. philSweet
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    philSweet Senior Member

    Just curious, and off topic, but how does the oil sump work? Does the air come in the top and take the oil out with it into a common airbox/sump?
  6. Lemans
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    Lemans Lemans

    Double power .. or half displacement .. or half the speed .. or a combination of a bit from all. (compared with a normal aspirated engine)

    Yes, a 'one' revolution pressure version ( as the drawing in the OP ) is theoretical able to deliver 1.8 bar if the engine is designed for it. We expect this to be 1.4 bar in the real world.
    If one-way valves are used, we can 'stock' the air from the 'lost' revolution in an air-box and in that case, the theoretical max. pressure is 2.2 bar – ( 1.8 bar expected in reality - volumetric efficiency up to 190%)

    We ran a 600 cc flat two prototype with an electric motor of 0.5 HP and we monitored a 1.8bar constant pressure in the air-box. This figure was used as ambient pressure indication in the Lotus Engine Engineering software and the gain in power was more than 20 HP.
    Must say that the engine did only 30% of his max. speed.
    I thing the engine need 10% max. of the extra power the crank deliver.

    Here I need to go for a bit of logic thinking.
    Specific fuel consumption vary a lot and depends on the rpm and throttle settings.
    If we look into the figures published all around the globe for all sorts of engines we see better figures if we allow the fuel enough time to burn.
    So, if the extra air is used to run the engine on lower rpm and a similar power output, I believe that the engine will run cleaner and more fuel efficient.
    Energy lost on valve train should be less and in situations that not all the power is needed,
    it's possible to set the second phase (pressurized phase) on hold. No compression needed – no power loss due to compressed air at all.

  7. Lemans
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    Lemans Lemans

    It all depends on size and engine speed.
    There is a total different approach. On slow running diesels it's possible to filter out the oil.
    Today's modern motorcycles showing us how to do this. Environmental regulations have boosted
    this technology.
    But...this is not the case if someone want to build a high revving petrol engine based upon this
    unusual 4-stroke cycle. In that case we also have a few options.
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