Aerospace Technic and Technology

Centrifugal compressors often operate at different capacities, so it is important to ensure their stable operation over a wide flow range. Stages with vaneless diffusers have several advantages compared to stages with other types of diffusers: they are more technologically advanced to manufacture, and more uniform pressure distribution behind the impeller improves the dynamics of the rotor. At low flows, due to the occurrence of a rotating stall and surge, the efficiency of stages with vaneless diffusers rapidly decreases. The occurrence of unstable operating modes of centrifugal compressor stages at low flow rates is associated with the appearance of developed backflows in the flow part. To expand the range of stable operation of the stages, it is necessary to use methods of flow separation control. Separation of the flow can be controlled either by special profiling the flow part channels or by actively influencing the flow, for example, by injecting gas. To solve this problem, a mathematical model of the gas flow in a vaneless diffuser with gas injection is developed. The characteristics and parameters of the flow in the vaneless diffusers with various meridional profiles with and without injecting gas were calculated. A comparison of the calculated and experimental characteristics of the vaneless diffusers and flow parameters in diffusers with different geometries and with different injection modes confirms the adequacy of the mathematical model. Investigations have confirmed the possibility of improving the characteristics of the stages of centrifugal compressors through the use of vaneless diffusers and diffusers with gas injection. Gas injection diffusers extend the stable operation range of the stages. The use of gas injection in a vaneless diffuser allows reducing the power consumption during antisurge control in comparison with the widespread bypass suction system at the entrance to the impeller

centrifugal compressor; vaneless diffuser; surge; investigation

Seleznev, K. P., Galerkin, Y.B. Centrifugal compressors [Centrobegnye kompressory]. Mashinostroenie – Mechanical engineering, 1982. 271 p.

Jansen, W. Rotating Stall in a Radial Vaneless Diffuser. J. Basic. Eng., 1964, vol. 86, pp. 750–758.

Kalinkevich, M., Ihnatenko, V., Shcherbakov, O. Investigation of the Gas Flow in the Vaneless Diffusers of the Centrifugal Compressors. International Conference on Compressors and their Systems 2011, City University London, UK, 5–6 September, 2011, pp. 51–60.

Kalinkevich, M., Shcherbakov, O., Ihnatenko, V. Investigation of Gas Flow with Injection in Vaneless Diffuser of Centrifugal Compressor. 8th International Conference on Compressors and their Systems, City University London, UK, 9–10 September 2013, pp. 501–510.

Kalinkevich, M., Shcherbakov, O. Numerical Modeling of the Flow in a Vaneless Diffuser of Centrifugal Compressor Stage. ISRN Mechanical Engineering, vol. 2013. 9 p. Article ID 602384.

Senoo, Y., Kinoshita, Y. Limits of Rotating Stall and Stall in Vaneless Diffusers of Centrifugal Compressors. ASME Paper No. 78-GT-19, 1978.

Skoch, G. J. Experimental Investigation of Centrifugal Compressor Stabilization Techniques. ASME J. Turbomachinery, 2003, vol. 125, pp. 704–713.