Peter Stickney > On Friday 15 July 2005 06:45, Vivian Meazza wrote: > > Josh Babcock > > > > > Vivian Meazza wrote: > > > > > > > > > > > Josh Babcock ought to be asking for the turbo charger for the > B29 now, > > > but > > > > hasn't yet (perhaps he's now using JSBSim?). I've been unable to > find > > > much > > > > available on the web for the Wright R-3350. I'm doing some work > on the > > > > aircraft carrier right now, but I've done some preparation for > the turbo > > > > simulation. > > > > > > Nope, I've just been busy with animations and other non-fgfs > stuff. I > > > don't have much data on the R-3350-23, but I do have the pilot's > manual > > > and a lot of web sites. If someone is offering to help with the > engines > > > I would love it. I am available to give all the info I have. I > don't > > > really feel I know enough about engines to do this properly > myself. > > > > If by 'someone' you mean me, then I guess I should help here. I need > some > > thing to test my putative modifications to YASim on anyway. > > > > I need a few hard numbers, which perhaps you could give me or point > me at a > > suitable web site/s: > > From a variety of sources, including the FAA Type Certificate Data > Sheet E-218 (Wright Double Cyclone C18BA series) and the 1950 edition > of "Model Designations of USAF Aircraft Engines". > > > 1. propeller gearing. > 0.35:1 > > > 2. max manifold pressure. > Now - that will depend on the specific rating. Exceeding the > allowable boost for an RPM/Mixture combination is Very, Very Bad. (As > in, as the P2V Manual puts it, "Trouble is indicated by internal > engine parts exiting teh exhaust stacks." > > > 3. full throttle altitude which may also be described as the > critical > > altitude. > > Military Power - 2200 HP/2800 RPM/ 44" Hg / SL-25,000' 15 Minute > limit > For the engine and turbosupercharger combination. > Without the turbo - (Mechanical blower only), the ratings were: > 2200 HP/2800 RPM/ 44" Hg /Sea Level > 2200 HP/2800 RPM/ 42" Hg / 7,000'. > > Note the decrease in MAP as altitude increses. Wright Engines from > teh late 1930s on were rated to a constant power, not a constnat > Manifold Pressure. As altitude increased, Temperature and Back > Pressure (Not relevant for the turbo) decreased, giving more power > for a given MAP. MAP was decreased to hold constant power. > > > > 4. the rated HP and the rated altitude. > > Normal Power - 2000 HP/2400R RPM/ 42" Hg/ SL-25,000' Continuous > (Turbo) > 2000 HP/2400 RPM/42" Hg/ Sea Level > 2000 HP/2400 ROM/41" Hg/ 4200' on the Mechanical blower only. > > > 5. take-off HP. > > 2200 HP/2800 RPM / 44" Hg > > > 6. Copies of the relevant pages of the Pilot's Manual. Post these > somewhere > > that I can access/fetch. Particularly any description of the > variable boost > > control. > > That was the FE's job. The supercharger system of a B-29, or any > other turbosupercharged airplane worked like this: (Well, was > supposed to work like this - Early B-17s and B-24s with the > mechanical oil pressure driven turboregulators required more > fiddling, but the electronic turboregulators used on later -17s, 24s, > P-38s, P-47s, B-29s and subsequent airplanes did work like this) > > There was a potentiometer dial on the turboregulator control box that > was calibrated from "0" to "10". This selected the amount of output. > from the turbo system as a whole, "0" being no output. The turbos > supplied air to the inlet of the engine's mechanical supercharger at > slightly over sea level ambient (29.92" on a Standard Day). This was > done to keep the turbo moving, so that it didn't freeze up due to > poor lubrication at Sea Level. The engine's throttle was set to > provide whatever power conditions were required, and as the airplane > climbed, the tubo's "Volume Control" was tweaked to keep providing > its sea level conditions to the engine's supercharger. The > Turboregulator governed on the selected pressure rise (The "Volume" > and turbo RPM and, often, bearing temperature. The Pilot of Flight > Engineer had no indication, or control over the turbo except the > potentiometer. As far as the engine was concerned, it was sitting > happily at Sea Level the whole time. Once it had reached the point > where the turbosupercharger/mechanical blow couldn't supply the > proper power conditions any more, power dropped off normally. > > I don't know, but it sound like you could be making things a bit more > complicated than they were. The Turbos were basically Black Boxes. > There wasn't anything more to do with them but set them to the > appropriate pressure rise & let them go. >
Very helpful. I think you will find that the turbo pressure was controlled by the pilot, at least at critical point of the flight. While the pilot can regard the turbo as a black box, we need to know a little more about it so that the FDM can be set up correctly. This is the first reference that I have seen to a turbo/mechanical blower combination. I would be interested in seeing your source. This is for the R-3350-23? Thanks Vivian _______________________________________________ Flightgear-devel mailing list [email protected] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
