This paper reports on the early development of a method to detect the approach of surge in centrifugal compressors, so that operating flow margins used to avoid surge can be reduced. This development effort is supported by the Department of Energy’s Natural Gas Infrastructure Program, with co-funding and technical assistance from the Gas Machinery Research Council and Siemens Energy and Automation Inc. Centrifugal compressors and flexible operations are increasingly important in the natural gas industry. Surge, which can unexpectedly occur at low flows, disrupts gas deliveries and can cause serious damage in a compressor such that it must be avoided. Current control methods require a significant surge margin and result in excess recycled flow, loss of efficiency, and wasted energy. A new method of near-surge detection, based on measurements of internal flow changes, has been identified and is being developed. Data from tests on a small laboratory compressor will be shown, and plans for field tests will be presented. This new method is not dependent on operating maps or an estimated surge line, and in contrast to current methods, provides a progressive signal, which can be used to directly control the surge margin. The development of an internal flow sensor and a method to implement this direct surge control is presented in this paper. This new method will reduce surge margins, wasted fuel gas or lost energy, excess emissions, calibration time, and operating expenses.
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