Engine Sim - Burn Duration

[Ben Beacock]

I'm working on the engine sim in Ricardo Wave and I'm wondering if anyone has worked out or tested for the burn duration of the charge at different RPM points (under full load). I'm trying to use our ignition timing data but the only way to enter them is by the CA50 50% burn point and I need the burn duration to calculate that. The manual hints at in-cylinder temp testing to derive the data-- which we are not set up for.

[Ben Beacock]

I'm working on the engine sim in Ricardo Wave and I'm wondering if anyone has worked out or tested for the burn duration of the charge at different RPM points (under full load). I'm trying to use our ignition timing data but the only way to enter them is by the CA50 50% burn point and I need the burn duration to calculate that. The manual hints at in-cylinder temp testing to derive the data-- which we are not set up for.

[Jersey Tom]

I would say the better question is.. why are you trying to determine burn time? I would imagine that would be damn hard to do at this level.

What is your goal of your Ricardo analysis. Does it need to be accurately qualitative, or just quantitative with the hard numbers coming from testing? Are there other variables to test which will be more useful?

[Ben Beacock]

my goal is to find out how the ignition timing affects power output in simulation and comparing it with the dyno data. I'm hoping to get some correlation without getting into the SI turbulent flame and knock modelling properties. I guess that will be my next step if I can't figure out the burn duration.

[Jersey Tom]

Interesting. Whats the end goal? Seems like a hard thing to model and really easy to get experimentally. I'd save Ricardo for intake, exhaust, cam design. Way more expensive and difficult to iterate on experimentally.

[murpia]

Burn-rate (mass-fraction burn) and heat release are usually determined by in-cylinder pressure measurement, often an expensive thing to measure.
I believe there are a number of empirical / approximate methods to do this, one I am aware of is 'Rassweiler-Withrow', maybe worth a Google, I dug up this:
http://www.visteon.com/utils/whitepapers/2003_01_3266.pdf
Regards, Ian

[Ben Beacock]

Thanks for the paper.. it looks like I might be able to use some of it. I also know what I'm searching for now (better terminology).

The end result of this is to be able to get a closer approximation of the spark timing map from simulation in order to save some dyno time.

[EfiOz]

AFR also also has a small effect on flame front propogation. Although it's nowhere near as profound as cylinder presuure effects.