Influence of sealing cavity geometries on flank clearance leakage and pressure imbalance of micro-scale transcritical CO2 scroll expander by CFD modelling

Yuheng Du, Michael Pekris and Guohong Tian

Energy, 2023, vol. 282, issue C

Abstract: For a micro-scale (< 10 kW) transcritical CO2 waste heat recovery power system, the scroll-type expander is a potential candidate. However, the scroll expander suffers from leakage and pressure imbalance issues because of the high-pressure working conditions. The current study designs twelve different sealing cavities based on the reference of labyrinth seals and presents a transient CFD analysis to investigate the flow behaviors. The results show that the sealing cavity has a positive impact on the machinery performance, where the isentropic efficiency improves from 0.907 % to 0.952 % for the single group. Increasing the height and cavity number of single-group sealing can improve the performance while enlarging the cavity spacing shows the opposite. There is no significant difference between the three different shapes of RST, ITST and RTST. However, the improvement in the instantaneous leakage ratio is remarkable, the leakage reduces from 55.3 % to 70.2 %. For the multi-group sealing cavity, the isentropic efficiency slightly improves to 0.982 %, and the pressure imbalance gets partially optimized. The locations of the sealing cavity are important to solve the pressure imbalance between two symmetrical working chambers. The paper suggests designing the upstream sealing cavity for a lower-pressure working process and downstream for a higher-pressure working process, which can ideally achieve the maximum pressure balance.

Keywords: Sealing cavity; Transcritical CO2 cycle; Scroll expander; Flank clearance (search for similar items in EconPapers)
Date: 2023
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:282:y:2023:i:c:s0360544223021692

DOI: 10.1016/j.energy.2023.128775

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