Gasser Math

here is some traditional imbert gasifier math from gasser guru Dutch John

calculating gas required to run an engine...


G = V x n x 0.5 x 0.48 x 0.72 [l/s]
                       60

G is the needed quantity of gas in liters per second
V is the engine displacement in liters
n is the rpm
0.5 is the four stroke factor
0.48 is the mixture composition (1: 1.1)
0.72 is the filling degree of the engine (assumption)
60 for the conversion to seconds

DJ's volvo example

Example: G = 2.32 x 2,750 x 0.5 x 0.48 x 0.72 = 18.4 [liter cold gas per second]
                                           60


calculating the restriction


d = square root from (4/pi x G/Vi)

d is the restriction diameter
pi is 3.142
G is quantity of cold gas per second
Vi is the superficial velocity being: 2.5 [m/s] = 25 [dm/s] for an Imbert


Example: d = square root from ((4/3,142) x (18,4/25)) = 0.97 [dm] = 97 [mm]


from this you can calculate the rest of the dimentions



all of that should get you in the ball park.

I build what i consider a modified imbert so I usually calculate restriction sizes and use that as my starting point.

Im sure it makes sense to you mate im afraid it's whoooshhhhhhh over my head :lol: I think my head its too full with other stuff so I got to leave room for updates to stuff I already know ....well that's my excuse ;) 

lol... it used to be over my head too....

i learned all that so one of my mentors could show me short cuts.

G is the needed quantity of gas in liters per second
V is the engine displacement in liters
n is the rpm in thousands of rpm

like G = V in liters x n in thousands x 3

so for calculating for my pickup truck

G = 5 x 2 x 3

G = 30 L/s of woodgas

and from that i can then calculate the restriction needed. i made a spreadsheet to help with math one day at a trade show... i hate math.

Too funny tritowns, your telling my life man, however I can see once you have the formula down it actually is quite simple.

The problem for most of us is grasping the formula, I appreciate you sharing it and as well describing how to understand it, once you have a firm grasp on the formula the rest is history and a lot of hard work and fabrication eh?

I do appreciate your thoughts on the subject matter and thanks for sharing them.
I am hoping to do a build this summer, just too darn cold out right now.

So what we are looking at here is how to formulate the amount of gas to produce at a given engine displacement and rpm rate.
So the rpm rate is the expected demand rate correct?
I find this very exciting.

A whole new world!:>)

yup. you design for the average you intend to use. for a stationary system this is/is not hard to do. automobiles are a little more complicated.

there are lots of other things to take into consideration.

when i'm building a system i look at handling condensates, hearth insulation, handling ash, air preheat... in that order. and thats just the gasifier... filtering and cooling need to be taken care of.

Again thanks for the formula and the great diagram, will have to study this well.