A Computer Programmed Design Optimisation and Analysis of Compressor Impeller

Centrifugal compressors are most widely used in large capacity refrigeration and air conditioning plants. Its other applications include in gas turbines for air craft applications, diesel engine turbochargers, chemical and process industries, factory workshop air supplies etc. In refrigeration field these are suitable for high specific volume refrigerants or low pressure stages. They have been used commonly for R-11, R-12, R-113, R-500, R-717 and eco-friendly refrigerant R-134a. As it is a high speed rotary machine, a large volume can be handled by it and therefore, found extremely suitable for large capacity installations. The centrifugal compressor stage consisting of an impeller, a vaneless space and/or a vane diffuser is significantly influenced by the performance of impeller. Real flow is three dimensional, viscous, in stationary and more complex to analyze. Scope of the present work is to design an impeller of a centrifugal compressor used for a 400 ton capacity air-conditioning plant. Dimensions of the impeller are estimated by developing a computer code based on the jet-wake theory. Pressure ratio and mass flow rate of the refrigerants are arrived from the thermodynamic cycle analysis and these are taken as inputs to estimate the impeller geometry. The vapor compression cycle calculations are performed for different refrigerants such as R-12, R-500, R-134a and R-152a. An impeller for a 3.4 pressure ratio centrifugal compressor is designed with R-12. The methodology is suitable for an impeller for any other application. The present method is validated from geometry available in the literature. Predicted results are very encouraging when compared with the existing design.