# Investigation of the Effects of Different Working Fluids on Compressor Cascade Performance
###### Abstract  
The compressor of closed Brayton cycle (CBC) plant operating with working fluid other than air is a vital element of the energy conversion unit. However, due to insufficient understanding of the influence of the physical properties of working fluids on the performance of the compressor, the actual working conditions and design conditions of the compressor's performance deviate greatly. In this paper, the objective is to analyze the influence mechanism of the physical properties on the performance of the cascade of compressor (static pressure ratio and total pressure loss coefficient). Therefore, the impact of a specific heat ratio on the performance of the compressor cascade is studied utilizing carbon dioxide (\(\gamma=1.29\)), air and carbon monoxide (\(\gamma=1.4\)), argon and helium (\(\gamma=1.667\)). Moreover, the relationships of static pressure ratio and total pressure loss coefficient with physical properties of the working fluids are analyzed in the compressor cascade. It is established that a higher specific heat ratio fluid gives a higher coefficient of total pressure loss and static pressure ratio in contrast to smaller specific heat ratio at matching inlet Reynolds number and Mach number. physical properties; compressor cascade; specific heat ratio; closed Brayton cycle 2021 11 1989 11  
fluids. The performance reduction of 50-MW EVO [11] German power plant is due to the wrong compressor performance analysis. The influence of this problem is also obvious in the research and development of carbon dioxide compressor. The experimental research on the CO\({}_{2}\) compressor was conducted by Sandia laboratory in the United States [12] and Tokyo University of Technology [13; 14] in Japan. The CO\({}_{2}\) compressor did not achieve the expected efficiency due to the above-mentioned problem of the variation of physical properties of the working fluids. After nearly a hundred years of development, a set of design criteria, design experience and reference data for air compressor design have been established through experiments. It is time-consuming and not an economical job to conduct a lot of experiments on alternate working fluid compressors, re-establish design criteria and gather design experience. Therefore, designing a special working fluid compressor with reference to the design criteria of air the compressor has become an important research topic. In order to create a compatible performance transfer method, [PERSON] highlighted that the compressor curve changes with dissimilar working fluid because of the disparity in specific heat ratio [15; 16]. [PERSON] et al. similarity criteria were derived using non dimensionless differential equations and similarity comparisons [17; 18]. He believes that the similarity standards of dissimilar working fluids may be Pr, Re, Sr, Eu, Pe, \(\gamma\) and Br. Air compressor characteristic charts are founded on empirical relationships based on similarity principles. Eu and Re are more accurate than the empirical relationship founded on universal similarity principles such as Ma and Re as specific heat ratio in Eu is self-contained. [PERSON] and [PERSON] linked the stream features of air and helium at dissimilar Mach numbers [19]. They believe that air and helium specific heat ratios has an important effect in increasing Mach number. The flow variance increases as Mach number increases. Changes in the turbomachine characteristic with the change in specific heat ratio were analyzed by many scientists; so far, the analysis of the working fluid influence on characteristics of the compressor has not been logical and the influence of working fluid characteristics on the compressor stall has not been reported in the literature. It is necessary to study the impact of physical properties on compressor cascade characteristics because most of the experiments on air compressors are conducted utilizing cascades.