So it is kind of modelled like an air pump. Interesting method. BTW p0 =101325 Pa R = 287.05 Cp_air = 1004.68 gamma = 1.4
Handbook of Aviation fuel properties, third edition: net heat of combustion of AVGAS, all grades : min. 43.5 MJ/kg, 44 typical density of AVGAS: 710 at 15degC C_p_AVGAS = 2.065 kJ/kg K @20degC, approx linear to 2.710 @140degC hope this might improve accuracy (a bit), Cheers, Eric On 12/11/2012 07:35 PM, Ron Jensen wrote: > On Tuesday 11 December 2012 09:46:10 Eric van den Berg wrote: > >> I see. >> Looking at the code (I think) I can see you are trying calculate the >> pressure losses in the injector/throttle valve, "airbox" and inlet tubes. >> Using throttle position and engine speed (was expecting cylinder >> displacement here also). >> > The displacement is somewhat irrelevant in that it is a constant and can be > ignored. The modeler provides two data points; the pressure at full throttle > and maximum RPM, and the pressure at 0 throttle and idle RPM. These are used > to determine the impedance of the airbox and throttle respectively. In this > scheme, the engine is also treated as an impedance which varies with > ( 1 / engine speed ) giving infinite impedance at 0 RPM[1] and falling > towards, but never reaching, 0 impedance as engine speed increases. > > > We experimented with many other and more complicated intake models early on, > and this is the best behaved of the lot. > > >> Basically your MAP at idle is to low, thus the >> pressure loss too high. As 99% of the pressure loss comes from the >> injector/throttle position, I would say for idle power setting the injector >> air valve should be a bit more open? >> > > > >> I assume it is only calculated for indication and not for engine power >> calcs? >> > Actually, the manifold pressure is used in three ways in the power > calculations. First, it affects the mass flow rate. We assume an adiabatic > process so the loss in pressure is accompanied by a corresponding loss of > density. Second, the volumetric efficiency is reduced by the intake pressure > being less than the exhaust pressure further reducing the mass flow rate. > Finally, the pressure difference between intake and exhaust creates a direct > power loss as work is performed to pull and maintain the manifold pressure > drop. > > Ron > > [1] Note: Engine speed actually used is mean pistons speed not RPM. > > ------------------------------------------------------------------------------ > LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial > Remotely access PCs and mobile devices and provide instant support > Improve your efficiency, and focus on delivering more value-add services > Discover what IT Professionals Know. Rescue delivers > http://p.sf.net/sfu/logmein_12329d2d > _______________________________________________ > Flightgear-devel mailing list > Flightgear-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/flightgear-devel > > > ------------------------------------------------------------------------------ LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial Remotely access PCs and mobile devices and provide instant support Improve your efficiency, and focus on delivering more value-add services Discover what IT Professionals Know. Rescue delivers http://p.sf.net/sfu/logmein_12329d2d _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
