Formula 1 Simplified Math Model Attached

[RodRico]

I was cleaning up my engine folder after award of the last patent and found the very simple math model of a Formula One engine linked below. I built the model back in 2016 when first starting my engine design effort. At the time, I was especially interested in reconciling all the talk I saw about levers and how inefficient crankshafts are with the fact that simple crankshafts dominate internal combustion engine designs. The model served that purpose well by teaching me that cranks aren't all that inefficient insofar as the engine has good ring seal, doesn't suffer too much piston skirt friction, and uses affordable high load bearings (like common hydrodynamic journal bearings). It also taught me all the different ways of expressing engine work from pressure applied to a lever to simple change in pressure over change in volume yield the same answer (so there's no need to talk about levers and mechanical advantage). It's a simple model, but I learned something from it, and I suspect other folks just starting out may as well.

Link to model on my OneDrive:

https://1drv.ms/x/s!Asoi6UVD5DYagY38Ul3VlMfiwPtCOao?e=Z9635Z

P.S. Note the file is an Excel workbook with a .xlsx extension which means it has no macros (if it did, it would have the .xlsm extension). Regardless, I recommend running virus scan on all files downloaded from the internet.

 

[dmapguru]

I have been looking at the spreadsheet you posted (thanks for this, it is very interesting) with a view to adapting it to estimate the pressure vs crank angle of a large 4 cylinder motorcycle engine. I am trying to understand why the "Start Burn" setting appears to be after TDC, i.e. Start Burn is set to 369 degrees. Could you enlighten me as to why this value is not some value before top dead centre?

Thanks.
DG

 

[RodRico]

Start Burn is set to 369 degrees. Could you enlighten me as to why this value is not some value before top dead centre

The term "start burn" doesn't accurately represent the model's operation. It's really more like "average heat release." In a real engine, combustion does start before TDC, but the majority of heat release comes after. To model combustion accurately, a better heat release model is required. As it stands, the model divides total heat release by degrees and spreads it out evenly over the stated period. Incorporating a better heat release model wouldn't be hard to do, it just wasn't important to me at the time since my engine employs HCCI rather the spark ignition.

Below is a pressure trace from a Formula One cylinder taken from "Demands on Formula One Engines and Subsequent Development Strategies." Note the pressure peak occurs from TDC to about 14 degrees after TDC as reflected in the model. Obviously, a complete modeling of the curve sans compression pressure would be more accurate than the current method.