Method and apparatus for measuring the distance of a turbocompressor's operating point to the surge limit interface

摘要

A method and apparatus are disclosed for protecting turbocompressors from unstable flow conditions (surge and stall). To accomplish this, it is necessary to easily and accurately calculate a compressor's operating point and its distance from the interface between the surge region and the stable region-this interface is referred to as the Surge Limit Interface. The proximity of the operating point to the Surge Limit Interface is calculated using measurements of properties throughout the compressor-process system. It is crucial that the calculation be invariant to suction conditions, especially gas composition. Disclosed are three coordinates, Tr (reduced torque), Pr(reduced power), and Ne(equivalent speed). Each of these can be combined with other invariant parameters to construct coordinate systems in which to define the Surge Limit Interface and measure the distance of the operating point to that interface.