Anthony Holmes Furman

Detection Of Surge Precursors In Locomotive Turbocharger

Locomotive engine performance depends among other factors on turbocharger efficiency and operating range. The turbocharger operating range can be constrained at high pressure ratio by flow induced instabilities, namely surge, in the centrifugal compressor. The resulting loss of flow results in degraded engine performance, higher exhaust emissions, high turbocharger vibration and can lead to mechanical damage on the compressor and adjoining air handling equipment. While surge avoidance methods are available to restrict the operating point to lie well within a static surge-avoid-line of the compressor, these methods can unnecessarily restrict the operating range, resulting in loss of overall performance and fuel efficiency. Surge detection and control is a closed loop strategy where a surge avoidance system starts acting if the onset of surge is detected. Use of such a strategy allows running at reduced surge margin to permit higher pressure ratio across the compressor, at potentially higher compressor efficiency, and yields increased power output from the engine at reduced emissions and improved fuel efficiency. This paper discusses a systematic approach adopted to detect precursors to the surge phenomenon, based on experiments on full-scale turbochargers and the use of a real-time wavelet algorithm to detect precursors.

Rotor Dynamic Improvement for a Locomotive Turbocharger

Turbocharger designs typically incorporate fixed-geometry hydrodynamic bearings. These bearings are known to be prone to exhibit sub-synchronous vibration response. This self-induced sub-synchronous vibration component is due to stiffness cross-coupling in the bearings and is independent of the level of rotor unbalance. This type of vibration has been shown to have the potential to destabilize the rotor-bearing system and inducing rapid growth in the vibration amplitude that could lead to mechanical failure. The present work considers the bearing redesign for a locomotive turbocharger with the objective of eliminating sub-synchronous vibration components by increasing the threshold onset speed with no increase in cost or bearing size. The paper describes the characterization of the original design, the optimization of the new bearing design and the experimental validation. As shown in the results, the optimized bearing configuration eliminated the sub-synchronous vibration component within the turbocharger speed range.Copyright