Propane with forced air burner

Discussion in 'Burners and their construction' started by Rtsquirrel, Sep 30, 2018.

  1. Jason

    Jason Gold

    I love fire!:D
     
  2. bowlweevil

    bowlweevil Lead

    “but its just too damn easy to grab the duct tape and attach the hair dryer tomy reil burner.”
    can you explain this further please? I have a Reil burner and have tried to add air but couldn’t get good results.
    Thanks,
    Mark
     
  3. rocco

    rocco Silver

    If your Reil was burning properly naturally aspirated, you'd need to add more propane to get it to burn properly with forced air, that means either higher pressure or a bigger orifice.
     
    Tobho Mott likes this.
  4. bowlweevil

    bowlweevil Lead

    T
    That makes perfect sense but he didn’t mention an orifice change or any other change, just duct tape a blower on.
     
  5. rocco

    rocco Silver

    It just comes down to the air/fuel ratio, there is a fairly small optimal range, do something that changes one, you also need to change the other to maintain an appropriate ratio.
     
  6. master53yoda

    master53yoda Silver

    A properly adjusted burner will put out the same temperature flame as any other properly adjusted burner, if you need higher flame temp as for iron melts you will need to REDUCE the excess air, the only reason to add a blower is to provide enough air pressure to overcome the back pressure in the furnace. The larger the burner the more fuel and air needed to reach the same temperature, fuel is added by increasing the fuel pressure or the orifice size. You can get millions of BTUs out of low pressure gas if the orifice and piping is large enough. the higher fuel pressure is needed to get higher btus out of smaller burners. Remember temperature of the flame and the quantity of heat are not connected. The only effect the flame temperature has is the ability to deliver btus to the higher temperature metal. Heat transferred is based on the difference in temperature between the heat source in the mass being heated.

    Art B
     
    HT1 likes this.
  7. HT1

    HT1 Gold Banner Member

    never heard it said clearer

    Al2O3 seems to have the Most indepth info, Quite literally the Math , He gave me some extremely exact info in this thread http://forums.thehomefoundry.org/index.php?threads/larger-moya.780/
    sadly Covid messed up My new furnace plans... at least pushed them to the right, so I have nothing to show for all that good info

    V/r HT1
     
  8. metallab

    metallab Silver

    It looks indeed nice. But what I miss in this discussion is gas flow. The psi (or bar) does not tell much. The power is proportional to the amount of gas burning, assumed the combustion is complete and stoichiometric. I have both propane and natural gas. With propane I use 1-1.5 bar (15-22 psi) while natural gas is only 0.03 bar (0.5 psi), but both perform almost the same in the sense of heat and temperature. The orifice in my natural gas burner is much larger and, due to the much lower pressure, the speed is slower, but forced air eliminates this problem.
    Are there any users using a flow meter ?
     
  9. master53yoda

    master53yoda Silver

    gas flow is a product of pressure and orifice size. There are charts available that provide fuel flow with out using metering,

    Even in commercial applications we don't use fuel metering because the air ratio is adjusted based on co2 and o2 levels in the flue gasses as well as control of the firebox pressure.

    We can accomplish the same thing with our furnaces by adjusting the air flow for the highest flame temp, this would be with a hot furnace and no load or metal we are trying to melt. I set my burners up with a t-couple in the exhaust port, with the flame just leaving the furnace. The best amount of fuel and air will have a small flame rollout at maximum flame temperature, this will give the best fuel/air ratio for that furnace and burner. When we put in metal to melt it will lower the flue temp and probably have a little more flame rollout as we have reduced the furnace volume.
     
  10. garyhlucas

    garyhlucas Silver

    The Mifco burner has an internal venturi that sucks the low pressure gas into the higher pressure air flow.
     

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