On Tuesday 19 July 2005 12:29, Vivian Meazza wrote: > Peter Stickney > OK, so what we have here is a 2 stage supercharger. The first stage is the 2 > turbos and the second stage is the single stage gear-driven supercharger.
Right. That will hold for any other turbosupercharged airplane, other than some of the light airplanes, that you'll come across. > I have enough data now for a reasonable simulation, but to make it more > accurate, I wonder if you could describe the action of the supercharger > pressure regulator? I can model it as just controlling the manifold pressure > between 0 and full. I interpret 0.8 (#8 on the dial) as being the setting > for full throttle height (military power). Settings 9 and 10 are emergency > settings. Did the controller act on the throttle, or a control a wastegate > to adjust the turbos, or just dump pressure, or? The controller used the Manifold Pressure at the engine inlet manifold to control the turbo's output. If you opened the throttle, you got more output from the turbo. If you increased the RPM (Prop to Full Increase), the turboregulator noted the higher pressure coming from the engine-stage blower and cut the turbo back. (With a controllable pitch prop, especially a constant speed prop, the throttle and the RPM are decoupled. The prop conrols RPM by changing its pitch. The throttle controls torque, which is indicated as MAP or BMEP settings. The turbo's output was controlled via the wastegates in the exhaust end. It really wasn't that much of an issue - airplane engine power settings don't get changed much, or in any great range, even for fighters in combat, so any lag wasn't a big deal. Somebody mentioned having a "Failure Mode" if you turned the boost up to 11 for too long. My experience with turbosuperchargers (I haven't blown up any airplane turbos, but I've killed a few on cars) is that the usual failure mode when the bearing is overtemped (Which is what you'd be doing) is for it to freeze. It doean't block inlet of exhaust flow much, but your Critical Altitude will suddenly drop from 25,000' to 7,000', and you might also get a fire going. > > But that's not the only way to do it. I've been preparing a series of > > articles on supercharging reciprocating engines. Is there any > > interest for me to pull some of it out and present it here? > > Probably not here, but personally I would be _most_ interested in anything > you have on this subject. I'll be in touch. Jon Berndt suggested the JBSSim Newsletter. I'm looking into that, and a few other things. > I have been struck by the lack of detailed information on the web on the > R3350, a stark contrast to the Merlin/Griffon. Rolls has always had good press agents :). Actually, it's rather hard to find good data on most engines. (Including Merlins) It's one of those areas where details can count. > Thanks > > Vivian > > > > _______________________________________________ > Flightgear-devel mailing list > [email protected] > http://mail.flightgear.org/mailman/listinfo/flightgear-devel > 2f585eeea02e2c79d7b1d8c4963bae2d > _______________________________________________ Flightgear-devel mailing list [email protected] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
