Study Of The Effect Of Different Self-Circulating Casing Treatment Structures On The Performance Of Supercritical Carbon Dioxide Centrifugal Compressor

Supercritical carbon dioxide is a new trend in the cycle,which in combination with the Brayton cycle will be disruptive in the new generation of power generation,due to the unique properties of supercritical carbon dioxide,high density and low viscosity,resulting in low compression work and high thermal efficiency at moderate temperatures.This can effectively reduce the size and weight of the equipment,which stands out in many Brayton cycle power generation fields,and the centrifugal compressor is one of important core components,a wide and stable operating range is extremely important for it.In this paper,a 10 MW supercritical CO2 centrifugal compressor is used as the object of research,the research content includes: the causes of compressor flow instability,the comparison of the treatment of the self-circulating magazine at different locations,and influence of different geometric parameters of the self-circulating magazine on compressor.The CFD numerical simulation method has been validated.A three-dimensional reconstruction of the centrifugal compressor was carried out using the structural parameters published by Sandia Laboratories in the USA,and the simulation results were compared with the experimental data to verify the reliability of the numerical simulation in this paper.Using the CFD numerical simulation method proposed in this paper,the solid-wall magazine centrifugal compressor is simulated numerically at variable operating conditions(70% speed,80% speed,100% speed,110% speed),and the near-stall point of the compressor is analysed according to the trend of its performance curve and the flow field inside the compressor,and it is concluded that the stall of the compressor first appears in the diffuser,and the expansion stability mechanism is used to account for it,laying the foundation for the widening of the stall margin of the compressor.For the internal flow field of the compressor,different positions of the centrifugal compressor were treated as self-circulating magazines,and CFD numerical simulations were carried out,and the advantages and disadvantages of the self-circulating magazines at different positions were analyzed through the comparison of their performance curves and internal flow fields.by doing the magazine treatment at the impeller,the stall margin increases by 29.4%,but the efficiency and pressure ratio decrease,and by doing the magazine treatment at the diffuser,the stall margin increases by 11.7% and the efficiency increases,but the pressure ratio also decreases.According to the above situation,the internal flow field change law,using theoretical knowledge to explain the reasons for the expansion of stability.Finally,the geometry of the autocyclic magazine will be changed and CFD numerical simulations will be carried out using the method used in this paper to compare how different autocyclic magazine treatment structures affect the performance of the centrifugal compressor.On the basis of this,numerical simulations are carried out for a particular autocyclic magazine treatment with variable operating conditions(70% speed,80% speed,100% speed,110% speed)to show that this self-circulating casing structure is suitable for the supercritical CO2 centrifugal compressor in this paper.