On Tue, 2008-12-16 at 05:12 -0700, John Denker wrote: > OK, let's back up and take another look at this. [snip] > Let's start with some basic science. Consider a RW piston engine > with a _fixed_ impedance in the induction system. That means > no governor and some fixed throttle position, fixed for the > duration of the experiment. > > It is an exercise in elementary algebra to prove (subject to > mild assumptions) that as the engine rotation speeds up, the > engine power output goes up. To first order in rotation rate, > the power is proportional to rotation rate. To second order, > the power is less than proportional, because (due to the > impedance) the MAP goes down ... but this second-order term > never overtakes the first-order term.
Lets see. Ignoring the manifold pressure and just looking at the assertion that an increase in RPM always leads to an increase in HORSEPOWER, I did a google image search for RPM vs HORSEPOWER. Just a few random hits that disprove your assertion: http://home.comcast.net/~stevtecv6/dynos/NHT_30V6_HP_MD_j30eststock.jpg http://myzx5.virtualdojo.net/images/dyno/Stock-vs-Volant%5BHP-AFR%5D(RPM%20Base).jpg http://www.gurgen.com/clint/G35/2004.09.04%20-%20Dyno%20Day/Plots/GurgenPB%20-%20Output.jpg This one is particularly interesting, as it shows exactly what you described as an "error" in the model. That is the horsepower decreasing with increasing RPM below the red-line when throttled: http://reveg-catalog.tamu.edu/images/Appendix/Engine%20Speed%20Graph-2.jpg > This result is robust and insensitive to details such as > the design of the propeller. The propeller in this model is the only load on the engine. Without a proper c_power table and a suitable Ixx in propeller model, the piston model will not function correctly. Thanks for reading, Ron ------------------------------------------------------------------------------ SF.Net email is Sponsored by MIX09, March 18-20, 2009 in Las Vegas, Nevada. The future of the web can't happen without you. Join us at MIX09 to help pave the way to the Next Web now. Learn more and register at http://ad.doubleclick.net/clk;208669438;13503038;i?http://2009.visitmix.com/ _______________________________________________ Flightgear-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/flightgear-devel
