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Turbomachinery > Instability
Axial Skewed Slot Effect on Rotating Stall Inception in Axial Compresso
Axial compressors suffer from unstable phenomena such as surge and rotating stall. Rotating stall involve stall cells which rotate azimuthally (2-D).
Axial skewed slot
In this research axial skewed slot is installed on a single-stage low speed research compressor and at the same time stall inception pattern is changed by re-staggering the IGV. The research objective is to investigate the mechanisms of axial skewed slot effect on spike stall compressor and mode stall compressor.
Compressor characteristic curve
(black: no treatment, red : axial skewed slot, left :spike inception, right : mode inception)
Unsteady casing pressure inside slot
Turbo Heat Pump Surge Analysis
Heat pumps pump heat from a low temperature reservoir to a high temperature reservoir by adding work to the system. Such turbo heat pumps are used in large-scale cooling systems for buildings. Turbo heat pumps consist of a compressor, a condenser, an expansion valve, and an evaporator, and the working fluid is a refrigerant. In the case of large scale heat pump systems, centrifugal compressors are used, and they can suffer from surge. Surge is a one dimensional instability which occurs in compression systems and is characterized by oscillations of the total annulus averaged flow. When surge happens, systems can encounter performance degradation, noise and mechanical failure.
P-h diagram
Schematic of heat pump
This research consists of three objectives. First, to describe surge behavior in turbo heat pumps, a nonlinear surge model has been developed by a lumped- parameter method and has been verified by experiment. Second, to predict surge onset point, a linear stability model has been developed based on the nonlinear surge model, and it has been verified by experiment. Finally, surge control strategies to stabilize heat pump system against surge instability are being developed.
Experiment vs. Modelling prediction
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