Rationalization of Empirical Loss Coefficients and Their Application in One Dimensional Performance Prediction Procedures for Centrifugal Compressors

The flow through centrifugal compressors is often highly separated and fully three-dimensional. Modern computing techniques have not yet provided the ability to predict this three-dimensional separated flow. The design engineer has the need of a relatively simple performance prediction procedure in order to assess the potential of any proposed design. Consequently, a number of performance prediction procedures, with the general assumption of one-dimensional adiabatic flow, have been published. A common and essential feature of all these procedures is the use of empirical parameters in order to expand the one-dimensional flow into a description of the fully three-dimensional flow. These empirical parameters usually describe the loss mechanism and the flow deviation in any duct. Presented in footnote is a one-dimensional procedure which separated the fundamental gas dynamics from the empiricism used. Consequently, it is a relatively simple matter to apply alternative empirical parameters, and, more importantly, it is also possible for the design engineer to readily apply empirical relationships built up from his own experience. Unfortunately, numerous techniques are used to define the losses, and it may be necessary for the design engineer to redefine his own data in terms compatible with the computer program available to him.