Engine Power Output Simulator help

[Chriszz11]

Hi, I am currently working on software to estimate Power and torque output of an engine by user input information such as; Bore, Stroke, Cylinders, intake flow rate, head flow rate, Boost, valves per cylinder, cam duration and lift, Ignition timing and quite a few more. So far I have gotten to a point that i am struggling to estimate Volumetric efficiency at a given RPM. It automatically calculates the Theoretical CFM at all RPM. The issue I am having is how to estimate the ACTUAL flow rate into the cylinders to use to calculate VE. As of right now, my Torque will just continually rise past 10000 rpm because of the assumed 1.0 VE at all times(this can not happen). Any help would be greatly appreciated. Please take it easy on me as i am new to engineering and this forum as well. THANKS!

 

[bentwings2]

Try desktop dyno. It's very popular and quite accurate. The pro version adds many what it's.
It's data base is huge.

http://www.proracingsim.com/desktopdyno.htm

 

[GregLocock]

I'd have thought if you know intake flow rate, temp, and pressure, then all you need to know is the fuel flow rate and calorific value and you are good to go.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[Chriszz11]

Greg Locock, as far as the intake airflow goes, what you have to start is max airflow at .50" lift. So at say 3000rpm, if you should be flowing 300cfm and your intake can flow 390cfm, you might only be flowing 270cfm because of the lower volumetric efficiency you would be at. I hope I explained that will enough. I might have missed your point however.

 

[BrianPetersen]

There are quite a number of engine simulation software packages out there, ranging from simple to extremely complex. That is what is needed in order to do what you are looking for. Why are you writing another one instead of using what's already out there?

 

[Chriszz11]

It's just a project that I wanted to work on. I'm not making it just because I need the software. I'm doing to better understand the math and physics involved with engines. I also just wanted to do it.

 

[GregLocock]

I was pointing out that if you know the intake flow rate, as your first post said, then you already know your VE

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[Chriszz11]

My apologies for the misunderstanding. When I stated in the OP that the intake airflow was a given, I was referring to max flow. What I need is how much air the engine will actually flow at a given rpm. @2000rpm the engine will flow far less than @5000rpm.

 

[CWB1]

Not sure your overall vision for this, but calculating peak power and torque fairly accurately is a pretty basic calculation. Like anything else in life you can take this ad-infinitem or you can use fuel flow, energy density, and a few assumptions about losses due to heat rejection and combustion efficiency. Depending on the specific engine these will vary a bit, so you'll either need to make assumptions or test.