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    Discussion in 'The main mechanical design forum' started by ME_man, Sep 14, 2015.

    1. ME_man

      ME_man New Member

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      For a Mechanical Engineering Design Class Project my group must design and develop a trap to sense whether diesel or gasoline is being pumped into the tank on a diesel vehicle, and to prevent the incorrect fuel from getting into the fuel tank. The device must be completely independent from the gas pump at the station. So obvious things like fuel nozzle size cannot be used.

      Does anyone have any ideas on how we could detect whether its gas or diesel entering the tank, more specifically the tank filler neck. The goal is to block the tank off if incorrect fuel is detected.

      Thanks for any ideas or advice

      John
       
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    3. Dana

      Dana Well-Known Member

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      Measure the index of refraction of the incoming fuel? Incoming fuel first fills a little cup and the weight determines the fuel type? Let it flow through an orifice and the different viscosity will cause the flow rate to be different?

      Either way you need to accept a little of the potentially wrong fuel and store and/or dispose of it.
       
    4. maniacal_engineer

      maniacal_engineer Well-Known Member

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      maybe vapor pressure? that is something that I always notice - gas cars have a "whoosh" when the tank is opened, but diesel does not.
       
    5. K.I.S.S.

      K.I.S.S. Well-Known Member

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      A small gas pilot light at the aperture of the filler tube will provide an extremely effective (and loud) means of determining when petrol is being pumped as opposed to Diesel...[​IMG]
      But seriously, you might want to think about electrical conductivity - petroleum has the highest conductivity of all hydrocarbons in terms of Siemens/Meter - Diesel is quite significantly lower. There are many safe ways this can be measured in a deflagrable environment.
      Specific Gravity could also assist you, but only if you have a good reference standard for the type of Diesel being used, as this can vary quite widely - if it's of the higher SG type, then there will be a measurable difference. If you have a chamber of a pre-determined volume in the fuel feed pipe (probably close to the top of it in order to allow the fuel foaming agents to cut off the flow from the pump when the chamber is full), then the weight of this chamber could be measured in milliseconds (the larger the chamber, the more accurate the differentiation). If correct, then a valve at the bottom can open. Probably tricky to do this purely mechanically with diaphragms etc, so my guess would be electro-mechanically.
      As an afterthought, perhaps the simplest way would be chemically based. Something like a fusion link that's bonded with something like salt? It doesn't dissolve in petrol, but then again I think that it also doesn't dissolve in Diesel, so something else...
       

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