Ricardo Questions

[nathan s]

Hey guys,

I have been trying to learn Ricardo, and finally got some simulation going.

What I was don't understand is what some of the abbreviations in the output file mean. Here are some of them:
PHI, PHITOT, Uvariance, Pvariance, etc...

Is there a table or list of them somewhere? I found a table for the Sum file abbv.s but nothing for output.

Also, is it possible to have negative bhp and torque? http://fsae.com/groupee_common/emoticons/icon_biggrin.gif. I think I have a value wrong somewhere.

[nathan s]

Hey guys,

I have been trying to learn Ricardo, and finally got some simulation going.

What I was don't understand is what some of the abbreviations in the output file mean. Here are some of them:
PHI, PHITOT, Uvariance, Pvariance, etc...

Is there a table or list of them somewhere? I found a table for the Sum file abbv.s but nothing for output.

Also, is it possible to have negative bhp and torque? http://fsae.com/groupee_common/emoticons/icon_biggrin.gif. I think I have a value wrong somewhere.

[Marc Jaxa-Rozen]

Phi is the equivalence ratio, a.k.a the inverse of lambda for AFR measurement. The variance figures are just convergence indicators.

Dunno about that negative power thing...well, maybe your car would be really fast in reverse http://fsae.com/groupee_common/emoticons/icon_wink.gif

Marc Jaxa-Rozen
École Polytechnique de Montréal

[John Bucknell]

First thing to check if you have negative power is whether you are actually flowing any air. If your cam timing is out of whack, a duct has zero diameter, etc. you'll just be motoring the whole shebang.

Stick with it, you'll figure it out.

[Charlie]

The *.out file is not really an output file. It's more like a debugging file. Use your *.sum file for results and analysis. You can use numerous built in WAVE programs such as RPlot to graphically show your .sum file output, but I preferred to use excel with search and find functions to easily be able to compare to my test data.

If you really want to know what the .out file is saying, it's in the basic users manual. Most of the values are in the .sum table you speak of as well. In the .out file, only final values or ducts and y-juntions are shown. Also pressure variance between ducts and timestep variance are shown for debugging purposes. It's easier to get this stuff by running a visual through WAPP than sifting through a text file so I just ignore the .out file.

[nathan s]

Hey, thanks for the info guys. Now to go try it out.

Have a Merry Christmas!

[Bam Bam]

I'm not a ricardo guy but negative horsepower and torque occurs quite often on real engines.
Example engine braking.

Take your foot of the gas and their you have it. Negative shaft torque as the friction torque of the engine is higher than the indicated torque (torque generated through combustion)

[nathan s]

I think I figured out what it was. I had the data for the valves in wrong, and they were opening and closing at the same time...Not very effective for running an engine as it turns out http://fsae.com/groupee_common/emoticons/icon_razz.gif. Now I am just working on getting the data adjusted right.

Thanks for the help!