Andy Ross
> Vivian Meazza wrote: > > You certainly are! The Boost Control works by adjusting the > > _throttle_ (in accordance with reality and your earlier suggestion). > > Why not just use a solution setting that doesn't involve the boost > control cutout? Why? The Merlin has a Boost Control Cutout, and the code works. But you are still confused - the Boost Control replaces the function of the misnamed wastegate, controlling the manifold pressure by retarding the throttle. This was your proposal which I implemented with Melchior's assistance. > I'd think that a "flat out" solution would be most > likely wrong anyway -- that's where engines are going to vary the most > between installations. Choosing anything at the edge of a performance > envelope and expecting the conditions to hold in the middle is always > problematic. What's wrong with using a cruise value for the cruise > solution? I do use the cruise value - based on the full throttle altitude. It's fine. YASim provides a good solution. Very impressive. > > The patch in my previous email, combined with your recent cvs input > > does all that is required, both now and in preparation for the > > supercharger/turbo charger thing. If you can suggest a way of doing > > it using the existing code, then I'm listening. > > As I read it, though, your patch is currently a noop. All it does is > add a new configuration option and adjust the handling of the > wastegate in a way that will never make a difference in practice > (skipping the wastegate handling for superchargers is irrelevant -- > supercharged engines already have a very high wastegate setting that > cannot be reached by an engine, running or not). I'm afraid that you are quite, quite wrong here. Supercharged engines do not have a high wastegate setting, and it is readily reached by the running engine over much of its operating range. This is what the "full throttle height" means. The Merlin's Boost Control operates from sea level up to the full throttle height, which can be up to 22,000ft depending on model. > I'm not arguing against it in principle. I'm just saying that I'm > going to wait until we have a real issue that needs to be solved; > using the _running boolean (which just indicates whether fuel is being > burned) Actually it means that the magnetos are > O and engine rpm > 60, but of course you know that. But I'm going to revisit this. > is not the right mechanism long-term. Can you explain again, > really carefully, exactly what behavior this patch gives you that you > need right now? This patch does the following: a. ensures that the manifold pressure is ambient when the engine is not turning. b. allows a windmilling engine to develop supercharger/turbo pressure c. skips the wastegate if the parameter 'supercharger' is true so that the Boost Control function which _you_ suggested be written (in Nasal), and which Melchior and I spent several days writing and tuning, can operate instead of the wastegate function. d. It allows accurate data to be used in the wastegate parameter. While the wastegate function is skipped, the wastegate parameter still has to be entered accurately to allow YASim to solve properly. This patch really is needed to allow the Merlin engine simulation to work properly. With it in place it is possible to plug in the numbers from the contemporary performance curves and get a simulation which closely matches the published figures. I'm going to try to do some work on Josh's B29 engines next. Hope this answers all your queries. Vivian _______________________________________________ Flightgear-devel mailing list [email protected] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
