Direction for High-Performance Supercritical CO2 Centrifugal Compressor Design for Dry Cooled Supercritical CO2 Brayton Cycle

Abstract

To overcome the degradation of the cycle efficiency of a supercritical carbon dioxide (S-CO2) Brayton cycle with dry cooling, this study proposes an improved design of an S-CO2 centrifugal compressor. The conventional air centrifugal compressor can achieve higher efficiency as backsweep angle increases. However, the structural issue restricts the maximum allowable angle (−50~−56°). In this study, an S-CO2 centrifugal compressor performance was examined while changing the backward sweep angle at impeller exit to study if the previous optimum backsweep angle for an air centrifugal compressor is still valid when the fluid has changed. It is shown through an analysis that an S-CO2 centrifugal compressor can achieve the highest efficiency at −70° backsweep angle, which is greater than the typical design value. The S-CO2 centrifugal compressor is less restricted from a structural integrity issue because it has low relative Mach number regardless of the low sound speed near critical point (Tc = 304.11 K, Pc = 7377 kPa). It is also shown in the paper that the variation of compressibility factor does not impact on its total to total efficiency since its Mach number is still lower than unity. Finally, it is also shown that a backward sweep impeller can achieve higher pressure ratio and operate stably in wider range as the mass flow rate is decreased. As further works, the suggested concept will be validated by the structural analysis and the compressor performance test.

Supercritical CO2 Mixtures for Advanced Brayton Power Cycles in Line-Focusing Solar Power Plants

“…The turbomachine dimensions are constrained to the working fluid density [33,34]. If the density is increased, the compressor and turbine sizes will be minimized.…”

“…To summarize the results obtained, some working fluid properties which have a direct impact on the cycle performance and on the power cycle equipment detail design are shown in this table. The turbomachine dimensions are constrained to the working fluid density [33,34]. If the density is increased, the compressor and turbine sizes will be minimized.…”

A Methodology and Information System for Computing and Optimization of Impellers and Vanned Diffusers Geometry Parameters

“…There are works on the design of impellers with different blade shapes and different productivity in the literature [1]- [6]. There are three types of blades: backward curved blades with an entry angle β2 < 90°, radial exit blades (β2 = 90°), forward curved blades (β2 > 90°).…”

“…The impeller is the most important and critical part of the compressor. In works [1]- [6], considerable attention is paid to the design of impellers, the improvement and optimization of their geometric and operating parameters, gasdynamic calculation and CFD-modelling are carried out.…”

Flow Control of Radial Inlet Chamber and Downstream Effects on a Centrifugal Compressor Stage

“…Centrifugal compressors, as important general purpose equipment, are widely used in the aerospace, chemical, power and energy industries, but they are also highly energyconsuming machinery in industrial systems [1,2]. The devices that transport working fluids from the pipelines or the atmosphere to the impeller inlet are called inlet chambers, and radial inlet chambers are the key upstream component widely used in large-scale multistage centrifugal compressors due to the layout constraints of compact industrial systems [3,4]. However, compared with axial inlet ducts, the radial inlet chamber will introduce extra flow loss and distortions, which negatively influence the compressor's performance [5,6].…”