Exhaust thrust

[wyrmrider]

First car over two hundred, 204 at Alton Ill 1960 (Chris Karamesines not us), was running weed burners,
maybe Hydrazine

[SchmidtMotorWorks]

Lets do the math.

Taking the last upward turn of the zoomie pipe alone (the problems is much more complex though)
Using large #s 3" ID and 12" length in Z axis the volume is about 84 cubic inches
The air mass is 0.004 lbs, let's round up to 0.01 for fuel.
Let's say the exit velocity is 1,000 feet per second (I think it is much lower).
The force from the last turn in the pipe doesn't appear to be much.

Another place to look for down/side force from exhaust gas motion is from the acceleration of the gas in the exhaust valve seat throat during blow down. The acceleration is 100's of times higher there.

[Stan Weiss]

The governing principle is Newton's Third Law of Motion: "Every action has an equal and opposite reaction", so the force of the exhaust being directed upwards causes a reaction force driving the exhaust pipe downward.The equation is F = MA, so what's needed to compute it is the exhaust mass and the acceleration (from zero vertical velocity to whatever). Mass will be ingested air plus fuel, or 14/13 x CFM x 0.076 lb., but acceleration is a little trickier as it depends on exhaust gas velocity, which in turn depends on density and exit pipe diameter. For example, compared to a typical collector, a proper rocket nozzle would increase thrust at the expense of power lost to backpressure.

I have a policy of not doing math in public, so someone else can take it from here...

Bill,
A 600 ci engine @ 100% VE @ 6500 RPM - Inlet Temp 70 F - BP 29.92. A/F ratio 13:1 will have a Mass air flow of 5070 lbs/hr and a mass fuel flow of 390 lbs/hr.

Stan

[SchmidtMotorWorks]

Thinking about why funny cars swerve when a cylinder goes dead, might have more to do with aerodynamics.

[Malvn]

funny cars swerve when a cylinder goes dead, might have more to do with aerodynamics.

Are you able to do a Simulations with the CFD for the above ?? It would be really interesting to see that

[SchmidtMotorWorks]

funny cars swerve when a cylinder goes dead, might have more to do with aerodynamics.

Are you able to do a Simulations with the CFD for the above ?? It would be really interesting to see that

I am doing work for a FC team now but I don't have a model of the body, it is one of those things that I would like to do.
I have a list of instruments that I am working on now to measure a chain of clutch, tire and track values to help with clutch tuning.

[Malvn]

I am doing work for a FC team now but I don't have a model of the body, it is one of those things that I would like to do.

Darn I was getting really excited about seeing that in your CFD program

It does sound very interesting to me on how this CFD program really works
To be able to look at clutch settings airflow crankshaft designs etc.


My thoughts on why they swerve is the loss of Torque in one cylinder that was there then gone real quick causing a negative
torque steer plus the aerodynamics.

[SchmidtMotorWorks]

I am doing work for a FC team now but I don't have a model of the body, it is one of those things that I would like to do.

Darn I was getting really excited about seeing that in your CFD program

It does sound very interesting to me on how this CFD program really works
To be able to look at clutch settings airflow crankshaft designs etc.

CFD wouldn't be for the clutch. I am making actual machines to measure the friction on the red-hot discs and another machine to measure the pressure plate force and other instruments for tire and track friction.
Then a solver to pick clutch adjustments from that data.

Surprisingly the one of the most challenging parts of the project is making the machines so that they can fit in the trailer, be moved easily, run on the power from the generator. These projects are 1% idea, 99% work.

Any of this tech is available to learn and use at community colleges, even some high-schools have it now.

Here is a link to some classes in PA to get started.

http://www.hacc.edu/NonCredit/upload/Co ... hining.pdf

[Malvn]

Thanks for the link on classes in Pa

But that is to far from my actual Home

Although I have signed up for Classes on Fluid Dynamics for this up coming Fall


SchmidtMotorWorks

Just to let you know I Ment no pun or digs about the CFD

[SchmidtMotorWorks]

Thanks for the link on classes in Pa

But that is to far from my actual Home

Although I have signed up for Classes on Fluid Dynamics for this up coming Fall

Great decision!

[srq]

I was just reading about aerodynamics on a F1 tech forum (I should of copy and pasted it) and one member from a TF team said their exhausts can have as much as 800 lbs of downward force. I know these engines make some hellish power but does this sound right ?
Any thoughts from the TF guys ?

WB

[SchmidtMotorWorks]

I was just reading about aerodynamics on a F1 tech forum (I should of copy and pasted it) and one member from a TF team said their exhausts can have as much as 800 lbs of downward force. I know these engines make some hellish power but does this sound right ?
Any thoughts from the TF guys ?

WB

Most nitro guys think it does but the math shows otherwise at least as a result of the curved pipe shape.
There are plenty of physics issues that people in all levels of motorsports are mistaken about.
Frankly, very few people in the sport would take the time to pick up a calculator to check their beliefs.

[rookie]

As one crew man found out a few of years ago, it's enough to rip you pants clean off!
http://www.ar15.com/forums/t_1_5/1087115_.html

[SchmidtMotorWorks]

This looks like the instant where the exhaust was blew into his pants:

[SchmidtMotorWorks]

Here is after the car has passed, his pants don't seem to be off.