Turbomachinery selection: Generating the selection charts and extending their use beyond the conventional for cryogenic plants

Non-dimensional analysis of turbomachinery reviewed and presented in a nutshell. Momentum equation of the inward flow radial (IFR) turbine is used to correlate efficiency of the turbine with the parameters, specific speed (n_s) and specific diameter (d_s). The design points satisfying the momentum and energy equations simultaneously for the specific but common design case of c_u/u = 1, are extracted from the Balje charts. It is shown that for such a case d_s and the isentropic efficiency can directly be correlated with specific speed n_sfor constrained optimization studies of the cryogenic cycles. An attempt has been made to extend the use of the concept of n_s -d_s charts for selection and design of the cryogenic process cycles where the design demands maximum possible plant efficiency plant compactness and impurity management. As an elucidation of the concept, optimization and performance maps of a two stage reverse Brayton cycle based refrigerator are generated and presented.