Effect of the specific heat ratio on transonic axial compressor rotor performances

Abstract The choice of working fluids in closed cycle has significant effect on the performance of plant. Numbers of gases including noble gases are being researched for their optimum use as working fluid in closed cycle including air, carbon dioxide, helium, etc. Compressor performance map of air is not applicable for these gases, due to variation in specific heat ratio. In this paper, the effects of the specific heat ratio on the transonic axial compressor rotor performance are investigated using air (γ = 1.4), carbon dioxide (γ = 1.29) and helium (γ = 1.667) as working fluids using theoretical analysis and numerical validation. Special attentions are paid to the relationships between the total pressure ratio, adiabatic compression efficiency and surge margin of the transonic axial compressor rotors with the specific heat ratios of the working fluids. It is concluded that at identical inlet Mach number and Reynolds number, the working fluid having higher specific heat ratio has higher total pressure ratio, smaller stall corrected mass flow and higher adiabatic compression efficiency in comparison with smaller specific heat ratio.