Comparative Analysis of Diagonal and Centrifugal Compressors with Synergy Theory in Compressed Air Energy Storage System

Energy storage technology is an essential part of the efficient energy system.Compressed air energy storage(CAES)is considered to be one of the most promising large-scale physical energy storage technologies.It is favored because of its low-cost,long-life,environmentally friendly and low-carbon characteristics.The compressor is the core component of CAES,and the performance is critical to the overall system efficiency.That importance is not only reflected in the design point,but also in the continuous efficient operation under variable working conditions.The diagonal compressor is currently the focus of the developing large-scale CAES because of its stronger flow capacity compared with traditional centrifugal compressors.And the diagonal compressor has the higher single stage pressure ratio compared with axial compressors.In this paper,the full three dimensional numerical simulation technologies with synergy theory are used to compare and analyze the internal flow characteristics.The performance of the centrifugal and diagonal impellers that are optimized under the same requirements for large-scale CAES has been analyzed.The relationship between the internal flow characteristics and performance of the centrifugal and diagonal impellers with the change of mass flow rates and total inlet temperature is given qualitatively and quantitatively.Where the cosine value of the synergy angle is high,the local flow loss is large.The smaller proportion of the positive area is the pursuit of design.Through comparative analysis,it is concluded that the internal flow and performance changes of centrifugal and diagonal impellers are different.The results confirm the superiority and feasibility of the off-design performance of the diagonal compressor applied to the developing large-scale CAES.