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Centrifugal compressors are the most commonly used types of compressors in industry. Performance of compressor is one significant parameter to be first determined prior to its design and operation. Centrifugal compressor's is usually expressed in terms of flow, head, speed and efficiency. Determining centrifugal compressor's performance operation is however very costly, due to it requirement for testing after fabricating and manufacturing of the compressor. This research is addressed to predict the centrifugal compressor performance cheaply through a numerical simulation. The study was conducted at a specific off design parameter for designed mass flow rate of 0,98 kg/s of centrifugal compressor. It is a single stage centrifugal compressor with an impeller diameter of 236.24 mm and a diffuser outer diameter of 349.83 mm. The number of impeller blades is 18 and the number of diffuser blades is 6 with a diffuser inlet angle of 15⁰. The numerical simulation was established and validated with experimental study. The simulation was then carried at the range of operating mass flow representing varies operation condition. The results revealed that simulation model has been built to simulate the performance of the centrifugal compressor. The simulation results were validated and accepted at deviation below 5%. In addition, the simulation is enabling to generate performance curve in term of pressure ratio and efficiency with respect mass flow rate. Maximum efficiency of the designed centrifugal compressor occurs at a mass flow rate of 1 kg/s with a value of 80.83%. This numerical method is very promisingly to be further incorporated for industrial application for predicting the centrifugal compressor performance. [ABSTRACT FROM AUTHOR]

Impeller is a part of centrifugal compressor that has an important role in the pressure generation process. Differences in the shape and size of this component greatly affect the overall ability of the compressor to generate pressure. This research is focused on prediction of centrifugal compressor performance by varying the impeller outlet blade angle. The study was conducted at off design parameter of a single stage centrifugal compressor with an impeller diameter of 236.24 mm and a diffuser outer diameter of 349.83 mm. The number of impeller blades is 18 and the number of diffuser blades is 6 with impeller inlet blade angle (β1) of 42°, and impeller outlet blade angle (β2) of 50°. The maximum efficiency of the designed centrifugal compressor occurs at a mass flow rate of 0.993 kg/s with a value of 83.71%. Result of the numerical simulation shows that the higher value of β2, the higher pressure-ratio that can be produced under all mass flow rate condition. Compressor overall efficiency also increases with the increase of β2 value. However, higher value of β2 results in an increase of instability level of gas flow at impeller outlet and eventually backflow began to occur in the β2 value of 90° that would reduce the volumetric efficiency of the compressor. [ABSTRACT FROM AUTHOR]