Naca Duct for an Engine Air Intake and intake shape

[ssc351]

Hi Everyone,

First post! Great site! I have little or no knowledge on these topics so I would like to get started somewhere with this design project. I need to design a Naca duct intake for a closed cockpit racecar (one with a roof...like a sedan). FYI, the throttle body has about 20 in^2 of area and faces straight up.
Here are some of the constraints:
1.) The Naca duct must be facing with the bigger flat end of the cone towards the front of car.
2.) It must be at least 3" after the transition at the rear of the roof where the car begins to slope back down. No real limit as to how far down to put it. Is this is toughy since I have no real flow/aero data?
3.) It must be able to flow enough air to handle a V8 with 500hp.
4.)The air from the naca duct must proceed directly to the upper intake plenum...doesn't mean you can't shape it how you want.

For the Naca duct:

1.) How do I want to design this ie. length, depth, angle compared to sloping rear of car, etc?
2.) Where do I want to locate it?

For the intake post Naca duct:
1.) Do I want it to make an "S" Shape (like an Indy or F1 car) down to the throttle body? If so, what angles/degrees should I make everything relative to each other.

Obviously, I have some pretty specific questions but I guess I just need to get a general feel for the theory and basic design ideas and I can work out the numbers for myself...hopefully

Thanks for the help!

 

[ckenny]

NASA Technical Reports Server

Submerged Duct

 

[Dave K]

http://naca.central.cranfield.ac.uk/reports/1945/naca-acr-5i20.pdf

http://sports.racer.net/tech_info/aero/naca_profile_calculator.xls

-Dave
Everything should be designed as simple as possible, but not simpler.

 

[WhiteRabbit]

Placing the larger flat end of the NACA shape forward will not allow the advantages of the inlet duct to be utilized.

The diverging shape of the inlet duct opens to match the shape of the vortices at the tip of the inlet. This allows a center section of the airflow to remain relatively laminar and constant relative airspeed.

If you want to increase the inlet air pressure (Induction) you should pick a convergence shaped inlet.

With this in mind you should probably add an over mass flow rate bypass valve or a pressure regulator. However, most of the pressure regulators are very sensitive to FOD and contamination so you would have to put a filter prior to the regulator which would restrict your mass flow rate and induction pressure.