Modeling and Simulation of Flow Transients inside a Multi-Stage Axial-Centrifugal Compressor
Author(s)
Jing, Zhenhao
Advisor(s)
Neumeier, Yedidia
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Abstract
In this work, an unsteady mean line flow model for multi-stage axial and centrifugal compressors is developed, where the blade rows, i.e., rotors and stators, are modeled as successive diffusing stream tubes in their own stationary or rotating reference frames. Thus, the compressor flow is “driven” by the added velocity at frame transformations instead of being driven by a user-input aerodynamic force, which is perpendicular to the flow direction. The developed mean line flow model features a series of physics-based modeling approaches that distinguishes itself from most unsteady compressor models. The aforementioned frame transformations between stationary and rotating reference frames are accommodated by inter-domain boundary conditions (interfaces), which allow acoustic waves to propagate the discontinuity in flow properties created by the frame transformation. Such a discontinuity accommodated by the interfaces is also used as a compact loss zone to include various loss models intended to capture the individual physical phenomenon. Thus, the energy addition at frame transformations and the loss models jointly predict the compressor aerodynamic performance, hence removing the need for user-input compressor performance.
A series of steady-state and unsteady simulations are performed and presented. Several sensitivity studies on selected individual loss models are presented for steady-state simulations to reveal their influence. During compressor rig tests, the flow transients are simulated to investigate the surge process and choke/unchoke response. A novel rig test approach enabling measurement of equilibrium characteristics on the unstable side is proposed and simulated. In order to simulate compressor flow transient in real working conditions in a gas-turbine engine, a lumped-parameter combustor-turbine model is developed and coupled with the compressor model. Such an approach enabled the simulation of gas turbine transients, including fast engine acceleration and deceleration and the effects of heat transfer in those engine transients. A novel active energy management strategy, which uses an electric starter/generator (ES/G) to enhance gas turbine acceleration, is proposed and simulated. A similar approach using ES/G to assist recovery from surges is also examined by simulation, and the necessary ES/G power for such a task is evaluated.
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Date
2024-04-27
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Dissertation