What size nozzle for a 95 Dakota?

Small Engines Charcoal Gasification
#1

Hi all,

name’s Bryan. I’ve been lurking around a while, had a look at the book, and finally got a hold of a 95 Dakota. Unfortunately, it’s in a sorry state, bought it at a salvage auction, but thought it’d make a good test vehicle. I was thinking of starting out with a charcoal gasifier, hopefully to notch an easier success, but also because I’ve got some use for the waste heat from the charcoal-making. I like the Simple Fire design by Mr. Gary Gilmore as well as the Tracker implementation by Mr. Don Mannes.

Here’s my question: What sort of cross-section do I need for the nozzle if I go with a Don-style forge-type? I recall coming across a table posted by Mr. Koen Van Looken, but can’t find it anymore and have to admit I wasn’t all too sure on how to read it the first time around. I’d like to figure out how narrow to make the ring around the nozzle center in order to get the best air velocity & volume for the Dakota.

Thanks!

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#2

Hi Bryan, wellcome!

The nozzle(s) diameter is not as important at charcoal gasifiers as it is at wood gasifiers. But generaly, a 25m/s of air jet is considered optimal. I am a fan of a bit lower gas velocitys personaly, read bigger nozzles, but like l sayd, this is not cruicial. You can allso use multiple nozzles. This way the reactor can be lower becouse instead of one tall reaction zones, you end up with more space for the fuel.

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#3

Hi, Brian!

31.10. 2017
When talking of charcoal nozzles and blow velocity, it’s OK to remember that

the cold air needed for cold gas delivered is about 65%.

For woodgas it is 60%.

:::::::::::::::::::::::::::::::::::::::::::::::::::::::::

Flow
___________ = flow area

velocity

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or

Flow : velocity = flow area

:::::::::::::::::::::::::::::::::::::::::::::::::::::::::

If your Dakota has a 5,2 liter displacement motor, and

If you determine the top (wot) RPM to be 3000,

then,

l = liters displacement,

n = RPM in thousands,

3 = combined factors for 4 - cycle motors (always the same),

then,

l ¤ n ¤ 3 = net gas consumption / second

5,2 ¤ 3 ¤ 3 = 46,8 liters / second

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This is cold gas consumption, so now you can figure out the need for

gasification air, and the velocity you want!

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#4

The nozzle (tuyere) for my 1.8 liter has 4-11mm (7/16") holes and eats a gallon of charcoal every three miles. Your Dakota will have a much bigger appetite. Think about a very big and tall charcoal hopper.

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#5

Kristijan, thank you! Appreciate the thought regarding multiple nozzles, your comment, plus Bruce’s, has me thinking of how I’m gonna deal with the thirstyness of the V8 - hadn’t thought about that. I take it that wood has a greater energy content by volume vs charcoal?
++

Max, thank you! for the figures, I’ll have to store it in the chew-it-over part of my brain for now, forgive me but I don’t currently have the background to sort it out, give me a bit of time.
++

Bruce, thank you! Hmm, I take it that consumption figure of yours is for the '76 MGB?

Looking at Fuelly, looks like you get about 21/22 MPG on gas-
http://www.fuelly.com/car/mg/mgb?engineconfig_id=36&bodytype_id=5&submodel_id=

On the '95 V8 Dakota-
http://www.fuelly.com/car/dodge/dakota?engineconfig_id=124&bodytype_id=11&submodel_id=
looks like I can expect about 16 MPG. So … not as awful as I immediately thought, but yes, something I need to think about. I’m staying in town at the moment, but the farm’s nearly 30 miles out in the county.
++

All, I ended up finding that ‘table’ by Koen after all, turned out it was a spreadsheet. Looking on that, I can see he also there quotes the 25 m/s velocity that Kristijan referred to. In terms of the RPM figure to use therein, would someone be able to tell me if I should use the max rated HP figure for the Dakota or the max torque? Although, with plugging in the figures, looks like it’s just a few mm difference.

Thank you everyone!

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#6

Ouch, that’s ugly. Don’t know why some of that is bold. How to I get rid of that?
[never mind, sorted]

#7

Hi, Bryan!

1.11.2017

I hear that you are glowing of enthusiasm, and will probably feel bad when words of caution and calming are raining from the other side of the pool…
Others have had to endure it, but few have quit… ideas seem to improve.

When starting with a “new” vechicle, fundamental repairs and maintenance is first on the list. When wheels, suspension, brakes, transmission and motor tune-up is fixed, the “driving in the driver” can start.

To learn what RPM gives 60 — 70 mph on a plain road and long uphills is valuable when calculating the comming char- or woodgas installation.

The very same RPMs have to be used on “the gases”, if lack of torque does not force the driver to “kick down” for a lower gear and higer rpms.

On Chargas or woodgas that is often likely, as the motor gets only half of the oxygen compared to “liquid fuel driving”.

The available oxygen dictates the amount of fuel that can be burned…

Now while driving, you are usually having RPMs above the max torque point, and below the max power point.

That’s why i suggested to calculate a gasifier to “barely” satisfy the gas demand at the top power (WOT) RPM.

3000 RPM WOT seems to be the consumption the gasifier should satisfy, at least for long uphills.

Charcoal gasifiers are not so critical as woodgasers on low loads.

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#8

Hi, Bryan!

1.11.2017

In what way can I help a grown up person who starts to renovate and rebuild a fine pickup?

The 4 simple arithmetic methods are of course familiar, aswell as taking a percentage of a given digit number…

In post no:3 in this thread there is: 65% of the cold gas is originating in cold (combustion) air.

That is = 0,65 times the resulting (produced) gas.

Then the gas consumption of the assumed motor is straight forward calculated in a fundamental way.

(assumed as a 1:1 mix in the formula)

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Now going back to the gasifier, taking 65% of the calculated gas flow shows the airflow for the nozzle(s all together)

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Then, “the rule of three” gives the max velocity for the calculated air flow

as you provide the flow through area (in the nozzle-tips),

Calculated flow m3/s
____________________________ = velocity m/s

area m2

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or with a set velocity you get the flow-through area.

Calculated air flow m3/s
_____________________________ = m2 area

Planned velocity m/s

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When using multi nozzles you have to divide the flow area between the nozzles. Not diameters!

Hopefully this helps a bit…

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