This is off the main line direction in this thread as to the whys and wherefores this engine seems to be suffering from some "built-in" shortcoming(s), but I was wondering if one of you could address a few questions as to the failure mode of the LPT disk itself. As a non-engineer, I've been musing about the "normal" operating speed of these turbines vis-a-vis the rotational speed necessary for self-destruction. (I'm retired... and I can afford to play golf and muse)
My questions start with a very basic one, which is, in the quest for efficiency and low mass, are these units designed to spin in a near supersonic regime, or do they experience tip velocity excursions approaching SS, say at the highest power settings, like N1 does?
Its moot to the cause of this engines demise, but, regardless of whether the LPT may or may not ever operate near the "shock" regime, at some point after the output shaft separation, and prior to disk impingement with the stators, could the free wheeling disk (blades) have been almost instantly accelerated past Mach 1 prior to the disk burst point? If so, could the blades have failed first from "swallowed shock," their sequential departure thus initiating intolerable out of balance, and, therefor, premature disk rupture?
If management of near supersonic blade tip velocity is, in fact, a parameter in this engines software, its actions in this regime and any harmonic issues impinging on the bearing box would have been completely addressed... No surprises there, right?
My, oh, My! You all have an extremely interesting discussion on-going here.