An Approach to Prevent Tip-Out Surge in a Turbocharger Compressor
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Date
2025-05
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The Ohio State University
Abstract
At low mass flow rates, a turbocharger's performance is limited by compressor surge which is an instability characterized by self-sustained oscillations in the compression system. Compressor throttle valves (CTVs) are used to regulate compressor flow, and a rapid closure of the CTV is called a “tip-out”. Bypass valves are typically used to prevent surge during tip-outs by venting excess compressor exit pressure through an alternative path. To reduce complexity, however, there is interest in preventing surge without a bypass valve. One method is to optimize the CTV closure profile: earlier attempts on this approach focused on single tip-out cases where the profile was manually determined. The objective of this research was to prevent surge for a range of tip-outs without a bypass valve by controlling the closing profile of a CTV. A turbocharger test stand was first used to determine the CTV angles that resulted in surge for various rotational speeds. These CTV angles are called the “critical angles” and fall on the stability limit of the turbocharger. Thus, actual CTV angles smaller than the critical angle for a given rotational speed are expected to result in surge as further reducing the flow rate pushes the compressor into the unstable region. The controller was then implemented into LabVIEW, and it prevents surge by ensuring the actual CTV angle is never smaller than the critical angle for a given rotational speed. The results showed that surge was prevented for all tip-out cases automatically within a selected range. The controller was tuned such that the compressor operated near the surge boundary indicating that the closure time of the controlled CTV profiles is near optimal for the current logic implementation. This study benefits the automotive industry by demonstrating that turbochargers can be kept out of surge during tip-outs without a bypass valve.
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Keywords
Turbocharger, compressor, surge, control, throttle