Flow Investigations in the Crossover System of a Centrifugal Compressor Stage

Abstract

The performance of the crossover system of a centrifugal compressor stage consisting of static components of 180 0 U-bend, return channel vanes and exit ducting with a 90 0 bend is investigated. This study is confined to the assessment of performance of the crossover system by varying the shape of the return channel vanes. For this purpose two different types of Return Channel Vanes (RCV1 and RCV2) were experimentally investigated. The performance of the crossover system is discussed in terms of total pressure loss coefficient, static pressure recovery coefficient and vane surface pressure distribution. The experimentation was carried out on a test setup in which static swirl vanes were used to simulate the flow at the exit of an actual centrifugal compressor impeller with a design flow coefficient of 0.053. The swirl vanes are connected to a mechanism with which the flow angle at the inlet of U-bend could be altered. The measurements were taken at five different operating conditions varying from 70% to 120% of design flow rate. On an overall assessment RCV1 is found to give better performance in comparison to RCV2 for different U-bend inlet flow angles. The performance of RCV2 was verified using numerical studies with the help of a CFD Code. Three dimensional sector models were used for simulating the flow through the crossover system. The turbulence was predicted with standard k-ε, 2-equation model. The iso-Mach contour plots on different planes and development of secondary flows were visualized through this study.

Aerodynamic Studies in the Static Components of A Centrifugal Compressor Stage

“…The RCV3 vane trailing edge appears to have an effect on the nature of swirl angle distribution. Figure 8 shows the variation of total pressure loss coefficient for RCV3, which is also compared with that of RCV1 and RCV2 reported by Reddy et al (2010). The total pressure loss coefficient is obtained by dividing the average total pressure difference between the L-turn exit and the U-bend inlet with the average dynamic pressure at the U-bend inlet.…”

“…Aungier (2000Aungier ( , 1993 and Lüdtke (2004) presented some design guidelines for the design of return channel passages of a centrifugal compressor stage. Reddy, Murty, Dasgupta and Sharma (2010) reported experimental and numerical studies in the crossover system of a typical centrifugal compressor stage with two different configurations of return channel vanes: RCV1, and RCV2. In their study, the ensemble of the static components of the centrifugal compressor stage, i.e., the crossover bend, cascade of return channel vanes, and the exit L-turn ducting, was referred to as the "crossover system".…”

“…In the present study, the aerodynamic performance of the static components, i.e., the U-bend, cascade of return channel vanes, and the exit L-turn ducting, is presented with a modified return channel vane configuration (RCV3). The aerodynamic performance of RCV3 is compared with that of RCV2 and RCV1 reported by Reddy et al (2010). The numerical solution for the RCV3 configuration is obtained for the same operating conditions used in the study of RCV1 and RCV2.…”

The effects of the return channel geometry on the aerodynamic performance of a centrifugal compressor: A numerical study

“…Similarly, Reddy et al 24,25 compared the flow characteristics for three different models of the return system, in terms of the inlet blade angle, blade chord and blade thickness for a centrifugal compressor stage with the flow coefficient of 0.053 at the design and off-design points. The numerical results illustrated that increasing the negative incidence on the leading edge of the vaned return channel causes fluid acceleration up to 30% chord length from the leading edge on the suction side.…”