Automotive turbochargers are known to have operation into the self-excited unstable vibration region. In the past these instabilities have been accepted as unavoidable, but recent developments in analysis and instrumentation may make it possible to reduce or eliminate them. A test stand has been developed at Virginia Tech to measure the vibrations of a 3.9 liter diesel engine stock turbocharger with both stock floating bushing journal bearings and also custom design fixed geometry bearings. Vibration spectrum content clearly identifies the shaft instabilities and provides the basis for additional evaluation of current and future improved bearing design modifications. The current results, for a series of custom fixed geometry journal bearings, show a shift in the frequencies of the two unstable modes for the no load operating condition. These results can be compared to the linear analysis predicted instability frequencies to better understand the actual response of the high speed turbocharger. This paper documents the spectrum content for three different bearing designs and compares the results to a stock floating bush journal bearing result for the same no load operating condition.
We report a first demonstration for the application of quantum computing to heavy quarkonium spectroscopy study. Based on a Cornell-potential model for the heavy quark and antiquark system, we show how this Hamiltonian problem can be formulated and solved with the VQE approach on the IBM cloud quantum computing platform. Errors due to a global depolarizing noise channel are corrected with a zero-noise extrapolation method, resulting in good agreement with the expected value. We also extend the calculation to excited states on a noiseless quantum simulator by orthogonalization with respect to the ground state.
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