Tuesday, March 5, 2019

Seven Fat Cows 4.9: Gasifiers, problems

Kelly and Milo were stumped. There was no reason that corn shouldn’t work. In fact, it should be the ideal fuel.

They started the experiment with the test platform in the midrange. That is, with the air inlet holes nine inches above the reactor grate. The 60 horsepower motor of the tractor sputtered and barely kept running, much less having enough power to run the brushhog.

Attempts to run the test platform with the air inlet holes five inches above the reactor grate caused the motor to promptly stall out.

At thirteen inches the gasifier barely kept the motor running when the PTO was engaged and the brushhog running. That was with no load on the brushhog other than friction and the air blowing through it.

It was a puzzler.

Kelly, who had more experience with “primitive” engines, meaning engines with carburetors, said “It acts like it is starved for fuel.”

They took a break and drank some coffee as they watched the tractor struggle to run at the thirteen inch setup.

“I got an idea.” Milo said. He walked over to Kelly’s steel rack and pulled out a six foot long piece of fence top-rail. The pipe was almost one-and-a-half inches in diameter.

Milo made a couple of short, longitudinal cuts in one end of the pipe and bent out ‘petals’.

Milo wrapped some window screen around the modified end and secured it with a radiator hose clamp and the petals gave the clamps something to grip.

He held the pipe against the side of the barrel and put a wrap of tape around it to provide a sense of scale.

Then he cracked the lid to the hopper feeding corn to the reactor and started pushing the piece of pipe down, toward the reactor. The densely packed corn resisted the effort and Milo had to twist the pipe to drill down through.

“Whatchya thinking?” Kelly said.

“I think air flows through wood chips a lot more easily than through corn.” Milo said.

“I wonder if six holes are enough. And even if they are enough, how is that air going to get to the corn in the center of the reactor?” Milo said.

When Milo judged the buried end of the pipe was at the same level as the other air inlet holes, he stopped pushing it in. Then he walked back to his coffee cup to see what happened.

The motor’s operation started to smooth up in about a minute. Then it picked up speed and sounded healthy.

“You know, the hell of it is that you can make an adjustment to the gassifier and you won’t know if what you did is correct for a few minutes while the generator adjusts.” Kelly noted.

“Yeah, I can see why that old farmer said you didn’t want to do a lot of shifting, just run it flat out in low gear.” Milo said. “It takes too long to tweak the generator into what the engine wants.”

Kelly was scratching his head. “I think we need another prototype.”

“I think we should try fourteen inches, eighteen inches and twenty inches. I also think we should use your idea of inserting a lance but make it bigger, maybe two inch diameter pipe. We can always throttle it back.” Kelly said.

“Sounds like a plan.” Milo said as he turned off the tractor.

Then he pulled out the lance and put the air-tight cover over the hopper. It would take a while for it to cool down enough that it wouldn’t spontaneously restart.

Then Kelly and Milo started work on the second prototype.



  1. I am no expert on production has but I vagly remember reading a story years ago about it being used to power farm trucks in England during the war and having to stop at the bottom of the hill to stir up the fire to have enough power to make the hill. The whole story line has promise.

  2. I'm interested to see where this one ends up! :-D

  3. So...are you writing from experience? If so, there are a bunch of folks that would LOVE to see the finished project! Or are you just trying to encourage one of your many faithful readers to give it a try?

    1. Alas, no experience on this particular project.

      What I do have experience with is projects that required multiple iterations and engineers who had the foresight to think ahead and put just a *little* more complication in the test bed which allowed them to sweep through a far larger range of inputs.

      The "information" about shelled corn requiring more air and more time to gassify than wood waste is just an educated guess.