Abstract
A high-performance centrifugal compressor is needed for numerous industry applications nowadays. The radial gap ratio between the impeller and the diffuser vanes plays an important role in the improvement of the compressor performance. In this paper, the effects of the radial gap ratio on a high-pressure ratio centrifugal compressor are investigated using numerical simulations. The performance and the flow field are compared for six different radial gap ratios and five rotational speeds. The minimal radial gap ratio was 1.04 and the maximal was 1.14. Results showed that reducing the radial gap ratio decreases the choke mass flow rate. For the tip-speed Mach number (impeller inlet) with Mu < 1, the pressure recovery and the loss coefficients are not sensitive to the radial gap ratio. However, for Mu ≥ 1, the best radial gap ratio is 1.08 for the pressure recovery and the loss coefficients. Furthermore, the impeller pressure ratio and efficiency are reduced by increasing the radial gap ratio. Finally, the compressor efficiency was compared for different radial gap ratios. For Mu < 1, the radial gap ratio does not have noticeable effects. In comparison, the radial gap ratio of 1.08 has the best performance for Mu ≥ 1.
Highlights
Centrifugal compressors are widely used in industry [1] and small gas turbine engines.A high-pressure ratio will be the goal orientation for centrifugal compressors, as this leads to saving energy, reducing emission and raising power density [2]
The high-pressure ratio centrifugal compressors suffer from narrow stable flow range [5] and low efficiency [6]
The choke mass flow rate reduces with a reduction in the radial gap ratio
Summary
Centrifugal compressors are widely used in industry [1] and small gas turbine engines.A high-pressure ratio will be the goal orientation for centrifugal compressors, as this leads to saving energy, reducing emission and raising power density [2]. With increasing applications of high-pressure ratio centrifugal compressors, several institutes, such as German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) [3] and Mitsubishi Heavy Industries (MHI) [4], have conducted many studies researching them. The high-pressure ratio centrifugal compressors suffer from narrow stable flow range [5] and low efficiency [6]. To improve the performance of high-pressure ratio centrifugal compressors, a considerable of researchers have conducted several surveys. Rodgers and Sapiro [8] discussed the considerations for selecting the appropriate geometries in designing a high pressure ratio centrifugal compressor. Ebrahimi et al [10] and Zheng et al [11] investigated on the improvement of stable flow range in high-pressure ratio centrifugal compressors. Lin et al [12]
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