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Velocity stack design

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Wed Oct 21, 2015 9:13 am PostPost subject: Velocity stack design
nefarious
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I'm in the process of designing a simple nitrous system for the Westfield and trying to come up with a clever idea for minimising the flow disturbance from the injector nozzles.
The plan at the moment is to have a sandwich plate made to fit between the TBs and the manifold, and mount the injectors into that. But the nozzles protrude about 5mm into the velocity stack (do you still call it that beyond the butterfly?), and this will negatively impact flow for the majority of the time when the the nitrous system is inactive.
The initial thought was to "hide" the nozzles behind the butterfly spindles, but packaging considerations make this impossible on the centre two bodies.
Next idea was to recess them into a NACA duct-type shape in the inner wall of the sandwich plate.
I know some of you lot are hotter on your aerodynamics than me (Adam?) - anyone got any brighter ideas for an internal design which will allow good atomisation when the injectors are in use, but minimises the degree of obstruction when they're not?
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Wed Oct 21, 2015 9:28 am PostPost subject:
AK
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can you not get a different nozzle setup the can fit snug in a hole, and flush with the inner surface?

Or is that not possible due to....

Never really looked at the jets before but are they angled to spray the nitrous where you want it (towards combustion) rather than just a spray out the end of a tip?

Can you 'edit' the inlet manifold and weld in angled bosses like used for injectors
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Wed Oct 21, 2015 9:33 am PostPost subject:
AK
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ultimately I think the restriction would be none existent... maybe even help by making the air turbulent Laughing I remember finding these vortex/venturi 'devices' in the inlet of my Impreza when it was imported :S
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Wed Oct 21, 2015 9:38 am PostPost subject:
AK
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We use weld-on bungs to properly mount the nozzles and keep them high enough out of the airstream. There’s no disruption in the airflow, as there is with other types of nozzles that protrude into the port, and we’ve found there’s up to a 30 horsepower increase by keeping the nozzle out of the airflow


http://www.dragzine.com/features/pri-coverage/pri-2013-nitrous-express-shows-off-5-stage-squeeze-system/
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Wed Oct 21, 2015 9:39 am PostPost subject:
nefarious
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The nozzles are straight cylinder shapes with the jets pointing out of the side (i.e. in line with the air flow). I guess they're designed that way because the fuel and nitrous are already mixed prior to injection, and the evaporation of the nitrous handles the fuel atomisation issue (meaning that nozzle design/angle is less critical than a regular injector).

It might work to angle them backwards (so the jet points at c. 30 degrees to the airflow), and at least partially recess the 'cylinders' into the inner walls.

Any clever shapes to think about (e.g. NACA duct type things)? Given I'll be having the sandwich plate CNC'd, I can choose pretty much any design/injector angle I like.
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Wed Oct 21, 2015 9:42 am PostPost subject:
nefarious
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AK wrote:
Quote:
We use weld-on bungs to properly mount the nozzles and keep them high enough out of the airstream. There’s no disruption in the airflow, as there is with other types of nozzles that protrude into the port, and we’ve found there’s up to a 30 horsepower increase by keeping the nozzle out of the airflow


http://www.dragzine.com/features/pri-coverage/pri-2013-nitrous-express-shows-off-5-stage-squeeze-system/


Same problem as I'm trying to tackle, just without redesigning the whole system from scratch (project is supposed to just be a cheap bit of fun).

Oh, and I'm calling BS on that "30bhp increase" figure, unless they're talking about a 0.5% improvement on a 6000bhp drag engine.
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Last edited by nefarious on Wed Oct 21, 2015 10:00 am; edited 1 time in total
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Wed Oct 21, 2015 9:42 am PostPost subject:
AK
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